Acknowledgement for multiple user communication in a wlan

ABSTRACT

A first communication device generates respective media access control (MAC) protocol data units (MPDUs) that include respective data for a respective second communication devices, and determines respective resource units (RUs) via which at least some of the second communication devices are to transmit as part of an uplink (UL) orthogonal frequency division multiple access (OFDMA) physical layer (PHY) transmission to respectively acknowledge receipt of the respective MPDUs. The first communication device generates respective control frames that are configured to prompt the at least some of the second communication devices to transmit the UL OFDMA PHY transmission, and that include indicators of the RUs via which the at least some of the second communication devices are to transmit as part of the UL OFDMA PHY transmission. The first communication device generates and transmits a single multi user (MU) PHY data unit that includes i) the MPDUs, and ii) the control frames.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/997,033, now U.S. Pat. No. 10,470,185, entitled “Acknowledgement forMultiple User Communication in WLAN,” filed on Jun. 4, 2018, which is acontinuation of U.S. patent application Ser. No. 14/938,680, now U.S.Pat. No. 9,992,774, entitled “Acknowledgment for Multiple UserCommunication in a WLAN,” filed on Nov. 11, 2015, which claims thebenefit of the following U.S. Provisional Patent Applications:

-   -   U.S. Provisional Patent Application No. 62/078,169, entitled “MU        Acknowledge for DL MU MIMO/OFDMA,” filed on Nov. 11, 2014;    -   U.S. Provisional Patent Application No. 62/089,029, entitled        “Acknowledge for DL MU MIMO/OFDMA,” filed on Dec. 8, 2014;    -   U.S. Provisional Patent Application No. 62/148,659, entitled        “Acknowledge for DL MU MIMO/OFDMA,” filed on Apr. 16, 2015;    -   U.S. Provisional Patent Application No. 62/156,047, entitled        “Acknowledge for DL MU MIMO/OFDMA,” filed on May 1, 2015; and    -   U.S. Provisional Patent Application No. 62/204,169, entitled        “Acknowledge for DL MU MIMO/OFDMA,” filed on Aug. 12, 2015.

The disclosures of all of the patent applications referenced above arehereby incorporated by reference herein in their entireties.

Additionally, this application is related to U.S. patent applicationSer. No. 15/337,668, now U.S. Pat. No. 10,098,119, entitled“Acknowledgment for Multiple User Communication in a WLAN,” filed onOct. 28, 2016, which is hereby incorporated by reference herein in itsentirety.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to communication networks and,more particularly, to wireless local area networks that utilizeorthogonal frequency division multiplexing (OFDM).

BACKGROUND

WLANs have evolved rapidly over the past decade. Development of wirelesslocal area network (WLAN) standards such as the Institute for Electricaland Electronics Engineers (IEEE) 802.11a, 802.11b, 802.11g, and 802.11nStandards has improved single-user peak data throughput. For example,the IEEE 802.11b Standard specifies a single-user peak throughput of 11megabits per second (Mbps), the IEEE 802.11a and 802.11g Standardsspecify a single-user peak throughput of 54 Mbps, the IEEE 802.11nStandard specifies a single-user peak throughput of 600 Mbps, and theIEEE 802.11ac Standard specifies a single-user peak throughput in thegigabits per second (Gbps) range. Future standards promise to supportboth downlink (DL) and uplink (UL) multi-user (MU) transmissions, suchas orthogonal frequency division multiple access (OFDMA) transmissionsand multi-user multiple input multiple output (MU-MIMO) transmissions,and to provide even greater throughputs, such as throughputs in the tensof Gbps range.

SUMMARY

In an embodiment, a method for communicating in a wireless communicationnetwork includes: generating, at a first communication device,respective media access control (MAC) protocol data units (MPDUs), eachMPDU including respective data for a respective second communicationdevice among a plurality of second communication devices; determining,at the first communication device, respective resource units (RUs) viawhich at least some of the second communication devices are to transmitas part of an uplink (UL) orthogonal frequency division multiple access(OFDMA) physical layer (PHY) transmission to respectively acknowledgereceipt of the respective MPDUs, wherein the respective RUs correspondto respective frequency portions of a communication channel; generating,at the first communication device, respective control framescorresponding to at least some of the second communication devices,wherein the respective control frames are configured to prompt the atleast some of the second communication devices to transmit the UL OFDMAPHY transmission, and wherein the control frames include indicators ofthe RUs via which the at least some of the second communication devicesare to transmit as part of the UL OFDMA PHY transmission; generating, atthe first communication device, a single multi user (MU) PHY data unitthat includes i) the MPDUs, and ii) the control frames; transmitting, bythe first communication device and to the plurality of secondcommunication devices, the single MU PHY data unit; receiving, at thefirst communication device, the UL OFDMA PHY transmission from the atleast some of the second communication devices, the UL OFDMA PHYtransmission corresponding to an acknowledgment of at least some of theMPDUs by the at least some of the second communication devices, whereinthe UL OFDMA PHY transmission includes respective transmissions fromrespective second communication devices via respective RUs indicated bythe control frames in the single MU PHY data unit; and processing, atthe first communication device, the UL OFDMA PHY data unit to determinewhether the at least some of the second communication devices receivedthe respective MPDUs.

In another embodiment, an apparatus comprises: a network interfacedevice associated with a first communication device. The networkinterface device comprises one or more integrated circuit (IC) devicesconfigured to: generate respective media access control (MAC) protocoldata units (MPDUs), each MPDU including respective data for a respectivesecond communication device among a plurality of second communicationdevices; determine respective resource units (RUs) via which at leastsome of the second communication devices are to transmit as part of anuplink (UL) orthogonal frequency division multiple access (OFDMA)physical layer (PHY) transmission to respectively acknowledge receipt ofthe respective MPDUs, wherein the respective RUs correspond torespective frequency portions of a communication channel; generaterespective control frames corresponding to at least some of the secondcommunication devices, wherein the respective control frames areconfigured to prompt the at least some of the second communicationdevices to transmit the UL OFDMA PHY transmission, and wherein thecontrol frames include indicators of the RUs via which the at least someof the second communication devices are to transmit as part of the ULOFDMA PHY transmission; generate a single multi user (MU) PHY data unitthat includes i) the MPDUs, and ii) the control frames; transmit, to theplurality of second communication devices, the single MU PHY data unit;receive the UL OFDMA PHY transmission from the at least some of thesecond communication devices, the UL OFDMA PHY transmissioncorresponding to an acknowledgment of at least some of the MPDUs by theat least some of the second communication devices, wherein the UL OFDMAPHY transmission includes respective transmissions from respectivesecond communication devices via respective RUs indicated by the controlframes in the single MU PHY data unit; and process the UL OFDMA PHY dataunit to determine whether the at least some of the second communicationdevices received the respective MPDUs.

In yet another embodiment, a method includes: receiving, at a firstcommunication device and from a second communication device, i) a mediaaccess control (MAC) protocol data unit (MPDU) and ii) a control frame,wherein the MPDU and the control frame are included in a single downlink(DL) multi-user (MU) physical layer (PHY) data unit, wherein the controlframe is configured to prompt the first communication devices totransmit as part of an uplink (UL) orthogonal frequency divisionmultiple access (OFDMA) physical layer (PHY) transmission by the firstcommunication device and one or more third communication devices,wherein the control frame includes an indicator of a resource unit (RU)via which the first communication device is to transmit as part of theUL OFDMA PHY transmission, and wherein the RU corresponds to a frequencyportion of a communication channel; determining, at the firstcommunication device, a frequency subband in which the firstcommunication device is to transmit an acknowledgment frame as part ofthe UL OFDMA PHY transmission, the acknowledgment frame foracknowledging the MPDU from the second communication device, whereindetermining the frequency subband is performed using the indicator ofthe RU in the control frame; generating, at the first communicationdevice, a UL PHY data unit that includes the acknowledgment frame; andtransmitting, by the first communication device, the UL PHY data unit aspart of the UL OFDMA PHY transmission.

In still another embodiment, an apparatus comprises: a network interfacedevice associated with a first communication device. The networkinterface device include one or more integrate circuit (IC) devicesconfigured to: receive, from a second communication device, i) a mediaaccess control (MAC) protocol data unit (MPDU) and ii) a control frame,wherein the MPDU and the control frame are included in a single downlink(DL) multi-user (MU) physical layer (PHY) data unit, wherein the controlframe is configured to prompt the first communication devices totransmit as part of an uplink (UL) orthogonal frequency divisionmultiple access (OFDMA) physical layer (PHY) transmission by the firstcommunication device and one or more third communication devices,wherein the control frame includes an indicator of a resource unit (RU)via which the first communication device is to transmit as part of theUL OFDMA PHY transmission, and wherein the RU corresponds to a frequencyportion of a communication channel; determine a frequency subband inwhich the first communication device is to transmit an acknowledgmentframe as part of the UL OFDMA PHY transmission, the acknowledgment framefor acknowledging the MPDU from the second communication device, whereindetermining the frequency subband is performed using the indicator ofthe RU in the control frame; generate a UL PHY data unit that includesthe acknowledgment frame; and transmit the UL PHY data unit as part ofthe UL OFDMA PHY transmission.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example wireless local area network(WLAN), according to an embodiment.

FIG. 2 is a diagram of an example transmission sequence in a WLAN,according to an embodiment.

FIG. 3 is a diagram of another example transmission sequence in a WLAN,according to another embodiment.

FIG. 4 is a diagram of yet another example transmission sequence in aWLAN, according to an embodiment.

FIG. 5 is a diagram of still another example transmission sequence in aWLAN, according to an embodiment.

FIG. 6A is a diagram of another example transmission sequence in a WLAN,according to an embodiment.

FIG. 6B is a diagram of another example transmission sequence in a WLAN,according to an embodiment.

FIG. 7 is a diagram of an example multi-user downlink communicationframe, according to an embodiment.

FIG. 8A is a diagram of another example multi-user downlinkcommunication frame, according to an embodiment.

FIG. 8B is a diagram of another example multi-user downlinkcommunication frame, according to an embodiment.

FIG. 9A is a diagram of another example transmission sequence in a WLAN,according to an embodiment.

FIG. 9B is a diagram of another example transmission sequence in a WLAN,according to an embodiment.

FIG. 10 is a diagram of yet another example transmission sequence in aWLAN, according to an embodiment.

FIG. 11 is a diagram of still another example transmission sequence in aWLAN, according to an embodiment.

FIG. 12 is a diagram of an example multi-user downlink physical layerprotocol data unit, according to an embodiment.

FIG. 13 is a diagram of an example transmission sequence in a WLAN,according to an embodiment.

FIG. 14 is a diagram of another example transmission sequence in a WLAN,according to an embodiment.

FIG. 15 is a diagram of an example information element that may beincluded in a downlink transmission, where the information elementincludes information that indicates to the client devices how togenerate an OFDMA/MU-MIMO acknowledgment for an MU DL PPDU, according toan embodiment.

FIG. 16 is a diagram of an example resource allocation informationelement that includes information to indicate to the client devices howto generate an OFDMA/MU-MIMO acknowledgment for an MU DL PPDU, accordingto an embodiment.

FIG. 17A is a diagram of an example field that is used to indicate asub-band within an OFDMA transmission, where the sub-band corresponds toa transmission to/from a client device, according to an embodiment.

FIG. 17B is a diagram of is a diagram of an example field that is usedto indicate a sub-band within an OFDMA transmission and also one or morespatial streams, according to an embodiment.

FIG. 18A is a diagram of another example field that is used to indicatea sub-band within an OFDMA transmission, where the sub-band correspondsto a transmission to/from a client device, according to an embodiment.

FIG. 18B is a diagram of an example field that is used to indicate asub-band within an OFDMA transmission and also one or more spatialstreams, according to an embodiment.

FIG. 19 is a diagram of an example set of allowable resource units for agiven starting 20 MHz channel, according to an embodiment.

FIG. 20A is a diagram of an example A-MPDU including an ACK, accordingto an embodiment.

FIG. 20B is a diagram of an example A-MPDU including an ACK and aresource request, according to an embodiment.

FIG. 20C is a diagram of an example A-MPDU including an ACK and a SYNC,according to an embodiment.

FIGS. 21A and 21B are diagrams of example shortened A-MPDUs that omitfields of a regular A-MPDU, according to some embodiments.

FIG. 22 is a flow diagram of an example method of transmitting a MUtransmission, according to an embodiment.

FIG. 23 is a flow diagram of an example method of receiving a MUtransmission, according to an embodiment.

FIG. 24 is a flow diagram of an example method of transmitting a MUtransmission, according to an embodiment.

FIG. 25 is a flow diagram of an example method of receiving a MUtransmission, according to an embodiment.

FIG. 26 is a flow diagram of an example method of receiving a MUtransmission, according to an embodiment.

DETAILED DESCRIPTION

In embodiments described below, a wireless network device such as anaccess point (AP) of a wireless local area network (WLAN) simultaneouslytransmits independent data streams to multiple client stations(sometimes referred to herein as multi-user downlink (MU DL)) and/orreceives independent data streams simultaneously transmitted by multipleclient stations (sometimes referred to herein as multi-user uplink (MUUL)). For example, the AP transmits data for the multiple clients indifferent orthogonal frequency division multiplexing (OFDM) sub-channelsof an orthogonal frequency division multiple access (OFDMA)transmission, in an embodiment. Similarly, multiple client stationstransmit data to the AP simultaneously, in particular, each clientstation transmits data in a different OFDM sub-channel of an OFDMAtransmission, in an embodiment. In another embodiment, the AP transmitsdata for multiple client stations using different spatial streams of amulti-user multiple input multiple output (MU-MIMO) transmission.Similarly, multiple client stations transmit data to the APsimultaneously using different spatial streams within an MU-MIMOtransmission to the AP, in an embodiment. In some embodiments, OFDMA andMU-MIMO are both utilized in a single MU DL or MU UL transmission.

In an embodiment, after receiving a MU DL from the AP, each clientdevice acknowledges receipt of the MU DL by transmitting anacknowledgement frames to the AP. For example, in an embodiment, eachclient device transmits an acknowledgment via a respective subchannelblock, where the transmissions from the multiple client devices form anOFDMA acknowledgement frame that includes respective acknowledgementsfrom the different client stations in different blocks of OFDMsub-channels, in an embodiment. In another embodiment, each clientdevice transmits an acknowledgment via a respective set of one or morespatial streams, where the transmissions from the multiple clientdevices form a MU-MIMO acknowledgment frame that includes respectiveacknowledgements from different client stations transmitted in differentspatial streams.

The AP is configured to operate with client stations according to atleast a first communication protocol. The first communication protocolis sometimes referred to herein as “high efficiency WiFi,” “highefficiency WLAN,” “HEW” communication protocol, or IEEE 802.11axStandard. The first communication protocol supports OFDMA communicationbetween the AP and the client stations, in some embodiments. The firstcommunication protocol supports MU-MIMO communication between the AP andthe client stations, in some embodiments. In some embodiments, differentclient stations in the vicinity of the AP are configured to operateaccording to one or more other communication protocols that defineoperation in the same frequency band as the HEW communication protocolbut with generally lower data throughputs. The lower data throughputcommunication protocols (e.g., IEEE 802.11a, IEEE 802.11g, IEEE 802.11n,and/or IEEE 802.11ac) are collectively referred herein as “legacy”communication protocols. The legacy communication protocols do notsupport OFDMA communication and/or MU-MIMO communication, in someembodiments. The legacy communication protocols support DL OFDMAcommunication and/or DL MU-MIMO communication, bud do not support ULOFDMA and/or UL MU-MIMO, in some embodiments.

FIG. 1 is a block diagram of an example wireless local area network(WLAN) 10, according to an embodiment. An AP 14 includes a hostprocessor 15 coupled to a network interface 16. The network interfacedevice 16 includes a medium access control (MAC) processing unit 18 anda physical layer (PHY) processing unit 20. The PHY processing unit 20includes a plurality of transceivers 21, and the transceivers 21 arecoupled to a plurality of antennas 24. Although three transceivers 21and three antennas 24 are illustrated in FIG. 1, the AP 14 includesdifferent numbers (e.g., 1, 2, 4, 5, etc.) of transceivers 21 andantennas 24 in other embodiments. In an embodiment, the networkinterface device 16 includes one or more integrated circuit (IC)devices. For example, at least some of the functionality of the MACprocessing unit 18 and at least some of the functionality of the PHYprocessing unit 20 are implemented on a single IC device, according toan embodiment. As another example, at least some of the functionality ofthe MAC processing unit 18 is implemented on a first IC device, and atleast some of the functionality of the PHY processing unit 20 isimplemented on a second IC device, according to an embodiment.

The WLAN 10 includes a plurality of client stations 25. Although fourclient stations 25 are illustrated in FIG. 1, the WLAN 10 includesdifferent numbers (e.g., 1, 2, 3, 5, 6, etc.) of client stations 25 invarious scenarios and embodiments. Two or more of the client stations 25are configured to receive corresponding data streams that aretransmitted simultaneously by the AP 14. Additionally, two or more ofthe client stations 25 are configured to transmit corresponding datastreams to the AP 14 such that the AP 14 receives the data streamssimultaneously.

A client station 25-1 includes a host processor 26 coupled to a networkinterface 27. The network interface device 27 includes a MAC processingunit 28 and a PHY processing unit 29. The PHY processing unit 29includes a plurality of transceivers 30, and the transceivers 30 arecoupled to a plurality of antennas 34. Although three transceivers 30and three antennas 34 are illustrated in FIG. 1, the client station 25-1includes different numbers (e.g., 1, 2, 4, 5, etc.) of transceivers 30and antennas 34 in other embodiments. In an embodiment, the networkinterface device 27 includes one or more IC devices. For example, atleast some of the functionality of the MAC processing unit 28 and atleast some of the functionality of the PHY processing unit 29 areimplemented on a single IC device, according to an embodiment. Asanother example, at least some of the functionality of the MACprocessing unit 28 is implemented on a first IC device, and at leastsome of the functionality of the PHY processing unit 29 is implementedon a second IC device, according to an embodiment.

In an embodiment, one or more of the client stations 25-2, 25-3, and25-4 has a structure the same as or similar to the client station 25-1.In these embodiments, the client stations 25 structured like the clientstation 25-1 have the same or a different number of transceivers andantennas. For example, the client station 25-2 has only two transceiversand two antennas (not shown), according to an embodiment.

According to an embodiment, the client station 25-4 is a legacy clientstation that is not enabled to receive a data stream that is transmittedby the AP 14 simultaneously with other independent data streams as partof an OFDMA transmission to multiple client stations 25. Similarly,according to an embodiment, the legacy client station 25-4 is notenabled to transmit a data stream to the AP 14 as part of UL OFDMAtransmission from multiple client stations 25. According to anembodiment, the legacy client station 25-4 includes a PHY processingunit that is generally capable of receiving a data stream that istransmitted by the AP 14 simultaneously with other independent datastreams that are intended for other client stations 25. But the legacyclient station 25-4 includes a MAC processing unit that is not enabledwith MAC layer functions that support receiving the data stream that istransmitted by the AP 14 simultaneously with other independent datastreams that are intended for other client stations 25. According to anembodiment, the legacy client station 25-4 includes a PHY processingunit that is generally capable of transmitting a data stream to the AP14 at the same time that other client stations 25 transmit data to theAP 14. But the legacy client station 25-4 includes a MAC processing unitthat is not enabled with MAC layer functions that support transmitting adata stream to the AP 14 at the same time that other client stations 25transmit data to the AP 14.

In some embodiments, when an AP transmits a DL OFDMA communication frame(e.g., a physical layer (PHY) protocol data unit (PPDU)), the AP thenpolls multiple client devices prompting the client devices to transmitacknowledgements of the DL OFDMA communication frame. FIG. 2 is adiagram of an example transmission sequence 200 in a WLAN, such as theWLAN 10 of FIG. 1, according to an embodiment, in which an AP, such asthe AP 14, transmits a DL OFDMA communication frame to multiple clientstations, such as multiple ones of the client stations 25, during atransmission opportunity period (TXOP) 202.

The AP 14 generates and transmits a DL OFDMA communication frame 204, inan embodiment. In an embodiment, the communication frame 204 comprisesrespective data 206 for multiple client devices. In an illustrativeembodiment, the data 206 comprise respective aggregate media accesscontrol (MAC) protocol data units (A-MPDUs) 206. In an embodiment, thecommunication frame 204 spans a bandwidth of a primary channel (e.g., aprimary 20 MHz channel) of the WLAN 10 and multiple other secondarychannels (e.g., 20 MHz channels) of the WLAN 10, i.e., the communicationframe 204 spans a bandwidth of a composite channel comprising theprimary channel and one or more secondary channels.

In an embodiment, the different data 206 correspond to differentpositions (in terms of frequency) within the communication frame 204,where each position is indicated by an index. For example, in anembodiment, the index starts at the lowest (in frequency) portion of theaggregate channel and increases as frequency increases. In anotherembodiment, the index starts at the highest (in frequency) portion ofthe aggregate channel and decreases as frequency decreases. Referring tothe example illustrated in FIG. 2, in an embodiment, A-MPDU 206-1corresponds to a first position, A-MPDU 206-2 corresponds to a secondposition, etc. In some embodiments and/or scenarios, each positioncorresponds to a 20 MHz channel. In other embodiments and/or scenarios,each position may correspond to a single 20 MHz channel or a compositeof multiple 20 MHz channels. In other embodiments and/or scenarios, eachposition may correspond to a single 20 MHz channel, a composite ofmultiple 20 MHz channels, or different portions of a single 20 MHzchannel.

In an embodiment, the client device corresponding to the datatransmission in the first position (e.g., STA0 corresponding to A-MPDU206-1) generates and transmits an acknowledgment (ACK) frame or blockacknowledgment (BA) frame to the AP via an uplink (UL) channelresponsive to the communication frame 204. For example, in anembodiment, the client device corresponding to the data transmission inthe first position generates and transmits an ACK frame or BA frame adefined time period (e.g., a short interframe space (SIFS) or anothersuitable time period) after the end of the communication frame 204. Inan embodiment, the client device corresponding to the data transmissionin the first position generates an ACK frame or BA frame that spans a 20MHz channel, duplicates the ACK/BA frame in one or more other 20 MHzchannels, and simultaneously transmits the ACK/BA and the duplicates ofthe ACK/BA. For instance, in the example of FIG. 2, STA0 transmitsmultiple instances of a BA frame 208 in multiple 20 MHz channelscorresponding to the bandwidth of the communication frame 204. In someembodiments, the ACK/BA is formatted according to the HEW protocol. Insome embodiments, the ACK/BA is formatted according to a legacyprotocol.

After receiving the ACK/BA 208, the AP generates and transmits a BArequest (BAR) frame to prompt another client device (e.g., STA1) totransmit a BA to acknowledge the DL transmission 204. In an embodiment,the AP generates an BAR frame that spans a 20 MHz channel, duplicatesthe BAR frame in one or more other 20 MHz channels, and simultaneouslytransmits the BAR frame and the duplicates of the BAR frame. Forinstance, in the example of FIG. 2, the AP transmits multiple instancesof a BAR frame 212 in multiple 20 MHz channels corresponding to thebandwidth of the communication frame 204. In response to the BAR frame212, the corresponding client device (e.g., STA1) generates an ACK frameor BA frame that spans a 20 MHz channel, duplicates the ACK/BA frame inone or more other 20 MHz channels, and simultaneously transmits theACK/BA and the duplicates of the ACK/BA. For instance, in the example ofFIG. 2, STA1 transmits multiple instances of a BA frame 216 in multiple20 MHz channels corresponding to the bandwidth of the communicationframe 204.

After receiving the ACK/BA 216, the AP generates and transmits a BARframe to prompt another client device (e.g., STA2) to transmit a BA toacknowledge the DL transmission 204. In an embodiment, the AP generatesa BAR frame that spans a 20 MHz channel, duplicates the BAR frame in oneor more other 20 MHz channels, and simultaneously transmits the BARframe and the duplicates of the BAR frame. For instance, in the exampleof FIG. 2, the AP transmits multiple instances of a BAR frame 220 inmultiple 20 MHz channels corresponding to the bandwidth of thecommunication frame 204. In response to the BAR frame 220, thecorresponding client device (e.g., STA2) generates an ACK frame or BAframe that spans a 20 MHz channel, duplicates the ACK/BA frame in one ormore other 20 MHz channels, and simultaneously transmits the ACK/BA andthe duplicates of the ACK/BA. For instance, in the example of FIG. 2,STA2 transmits multiple instances of a BA frame 224 in multiple 20 MHzchannels corresponding to the bandwidth of the communication frame 204.

The process continues with the AP prompting ACKs/BAs from client devicesuntil the AP generates and transmits a BAR frame to prompt a finalclient device (e.g., STA(n−1)) to transmit a BA to acknowledge the DLtransmission 204. In an embodiment, the AP generates a BAR frame thatspans a 20 MHz channel, duplicates the BAR frame in one or more other 20MHz channels, and simultaneously transmits the BAR frame and theduplicates of the BAR frame. For instance, in the example of FIG. 2, theAP transmits multiple instances of a BAR frame 228 in multiple 20 MHzchannels corresponding to the bandwidth of the communication frame 204.In response to the BAR frame 228, the corresponding client device (e.g.,STA(n−1)) generates an ACK frame or BA frame that spans a 20 MHzchannel, duplicates the ACK/BA frame in one or more other 20 MHzchannels, and simultaneously transmits the ACK/BA and the duplicates ofthe ACK/BA. For instance, in the example of FIG. 2, STA(n−1) transmitsmultiple instances of a BA frame 232 in multiple 20 MHz channelscorresponding to the bandwidth of the communication frame 204.

As can be seen in FIG. 2, the process of the AP sequentially (in time)prompting multiple client stations to acknowledge a MU DL transmissionadds to channel overhead. Thus, in some embodiments, client stationssimultaneously acknowledge a MU DL transmission using orthogonalfrequency division multiple access (OFDMA) or multi-user, multipleinput, multiple output (MU-MIMO) techniques.

FIG. 3 is a diagram of an example transmission sequence 300 in a WLAN,such as the WLAN 10 of FIG. 1, according to an embodiment, in which anAP, such as the AP 14, transmits a DL OFDMA communication frame tomultiple client stations, such as multiple ones of the client stations25, during a TXOP 302.

The AP 14 generates and transmits a DL OFDMA communication frame 304, inan embodiment. In an embodiment, the communication frame 304 comprisesrespective data 306 for multiple client devices. In an illustrativeembodiment, the data 306 comprise respective A-MPDUs 306. In anembodiment, the communication frame 304 spans a bandwidth of a primarychannel (e.g., a primary 20 MHz channel) of the WLAN 10 and multipleother secondary channels (e.g., 20 MHz channels) of the WLAN 10, i.e.,the communication frame 304 spans a bandwidth of a composite channelcomprising the primary channel and one or more secondary channels.

In an embodiment, the different data 306 correspond to differentpositions (in terms of frequency) within the communication frame 304,where each position is indicated by an index. For example, in anembodiment, the index starts at the lowest (in frequency) portion of theaggregate channel and increases as frequency increases. In anotherembodiment, the index starts at the highest (in frequency) portion ofthe aggregate channel and decreases as frequency decreases. Referring tothe example illustrated in FIG. 3, in an embodiment, A-MPDU 306-1corresponds to a first position, A-MPDU 306-2 corresponds to a secondposition, etc. In some embodiments and/or scenarios, each positioncorresponds to a 20 MHz channel. In other embodiments and/or scenarios,each position may correspond to a single 20 MHz channel or a compositeof multiple 20 MHz channels. In other embodiments and/or scenarios, eachposition may correspond to a single 20 MHz channel, a composite ofmultiple 20 MHz channels, or different portions of a single 20 MHzchannel.

In an embodiment, each client device to which a data transmission 306corresponds generates and transmits an ACK or BA portion as part of anUL OFDMA transmission 312 responsive to the communication frame 304. Forexample, in an embodiment, each client device to which a datatransmission 306 corresponds generates and transmits an ACK or BAportion 316 a defined time period (e.g., a SIFS or another suitable timeperiod) after the end of the communication frame 304. In an embodiment,each client device generates and transmits an ACK or BA portion 316 in arespective frequency block within a communication channel spanned by theMU DL transmission. Comparing the transmission sequence 300 with thetransmission sequence 200 of FIG. 2, it can be seen that thetransmission sequence 300 requires less channel overhead for ACKs/BAsfrom a given number of multiple client stations.

In the example of FIG. 3, each ACK or BA portion 316 has a same durationin time. Thus, in some embodiments, the AP determines the duration ofthe UL OFDMA transmission 312 and indicates to the client devices theduration of the UL OFDMA transmission 312. Then, each client devicegenerates the respective portion 316 to have the indicated duration.

In the example of FIG. 3, the DL communication frame 304 and the UL ACKtransmission 312 are OFDMA transmissions. In some embodiments, one orboth of a DL communication frame and a corresponding UL ACK transmissionare MU-MIMO transmissions. For example, in an embodiment, the DLcommunication frame 304 is a MU-MIMO transmission and the UL ACKtransmission 312 is a MU-MIMO transmission. As another example, in anembodiment, the DL communication frame 304 is a MU-MIMO transmission andthe UL ACK transmission 312 is an OFDMA transmission. As anotherexample, in an embodiment, the DL communication frame 304 is an OFDMAtransmission and the UL ACK transmission 312 is a MU-MIMO transmission.Thus, although various examples are described herein in the context ofOFDMA transmissions, similar techniques are applicable to MU-MIMOtransmissions.

In some embodiments, both i) OFDMA/MU-MIMO ACKs and ii) poll based ACKsare utilized to acknowledge a single MU DL transmission. For instance,in some embodiments, one or more client devices are not configured totransmit UL OFDMA ACKs, and thus the AP polls such clients to promptthose clients to transmit ACKs. In some embodiments, the AP may decidethat one or more client devices should not participate in an UL OFDMAACK, and thus the AP polls such clients to prompt those clients totransmit ACKs. Similarly, in some embodiments, one or more clientdevices are not configured to transmit UL MU-MIMO ACKs, and thus the APpolls such clients to prompt those clients to transmit ACKs. In someembodiments, the AP may decide that one or more client devices shouldnot participate in an UL MU-MIMO ACK, and thus the AP polls such clientsto prompt those clients to transmit ACKs.

FIG. 4 is a diagram of an example transmission sequence 400 in a WLAN,such as the WLAN 10 of FIG. 1, according to an embodiment, in which anAP, such as the AP 14, transmits a DL OFDMA communication frame tomultiple client stations, such as multiple ones of the client stations25, during a TXOP 402.

The AP 14 generates and transmits a DL OFDMA communication frame 404, inan embodiment. In an embodiment, the communication frame 404 comprisesrespective data 406 for multiple client devices. In an illustrativeembodiment, the data 406 comprise respective A-MPDUs 406. In anembodiment, the communication frame 404 spans a bandwidth of a primarychannel (e.g., a primary 20 MHz channel) of the WLAN 10 and multipleother secondary channels (e.g., 20 MHz channels) of the WLAN 10, i.e.,the communication frame 404 spans a bandwidth of a composite channelcomprising the primary channel and one or more secondary channels.

In an embodiment, the different data 406 correspond to differentpositions (in terms of frequency) within the communication frame 404,where each position is indicated by an index. For example, in anembodiment, the index starts at the lowest (in frequency) portion of theaggregate channel and increases as frequency increases. In anotherembodiment, the index starts at the highest (in frequency) portion ofthe aggregate channel and decreases as frequency decreases. Referring tothe example illustrated in FIG. 4, in an embodiment, A-MPDU 406-1corresponds to a first position, A-MPDU 406-2 corresponds to a secondposition, etc. In some embodiments and/or scenarios, each positioncorresponds to a 20 MHz channel. In other embodiments and/or scenarios,each position may correspond to a single 20 MHz channel or a compositeof multiple 20 MHz channels. In other embodiments and/or scenarios, eachposition may correspond to a single 20 MHz channel, a composite ofmultiple 20 MHz channels, or different portions of a single 20 MHzchannel.

In an embodiment, some of the client devices to which data transmissions406 correspond generates and transmit respective ACK or BA portion aspart of an UL OFDMA transmission 412 responsive to the communicationframe 404. For example, in an embodiment, some client devices to whichdata transmissions 406 corresponds generate and transmit respective ACKor BA portions 416 a defined time period (e.g., a SIFS or anothersuitable time period) after the end of the communication frame 404. Inan embodiment, some client devices generate and transmit respective ACKor BA portions 416 in respective frequency block within a communicationchannel spanned by the MU DL transmission.

In the example of FIG. 4, STA0-STA3 participate in the OFDMAtransmission 412, while STA4 does not. STA0 generates and transmitsportion 416-1. STA1 generates and transmits portion 416-2. STA2generates and transmits portion 416-3. STA3 generates portion 416-4,duplicates portion 416-4, and transmits the portion 416-4 and theduplicate of portion 416-4 so that the UL OFDMA transmission 412 spansthe bandwidth of the DL OFDMA transmission 404.

After receiving the UL OFDMA transmission 412, the AP generates andtransmits a BAR frame to prompt the remaining client device (e.g., STA4)to transmit a BA to acknowledge the DL transmission 404. In anembodiment, the AP generates a BAR frame that spans a 20 MHz channel,duplicates the BAR frame in one or more other 20 MHz channels, andsimultaneously transmits the BAR frame and the duplicates of the BARframe. For instance, in the example of FIG. 4, the AP transmits multipleinstances of a BAR frame 420 in multiple 20 MHz channels correspondingto the bandwidth of the communication frame 404. In response to the BARframe 420, the corresponding client device (e.g., STA4) generates an ACKframe or BA frame that spans a 20 MHz channel, duplicates the ACK/BAframe in one or more other 20 MHz channels, and simultaneously transmitsthe ACK/BA and the duplicates of the ACK/BA. For instance, in theexample of FIG. 4, STA4 transmits multiple instances of a BA frame 424in multiple 20 MHz channels corresponding to the bandwidth of thecommunication frame 204.

FIG. 5 is a diagram of an example transmission sequence 500 in a WLAN,such as the WLAN 10 of FIG. 1, according to an embodiment, in which anAP, such as the AP 14, transmits a DL OFDMA communication frame tomultiple client stations, such as multiple ones of the client stations25, during a TXOP 502.

The AP 14 generates and transmits a DL OFDMA communication frame 504, inan embodiment. In an embodiment, the communication frame 504 comprisesrespective data 506 for multiple client devices. In an illustrativeembodiment, the data 506 comprise respective A-MPDUs 506, where eachA-MPDU 506 includes a respective control frame 508 for controlling MU ULtransmissions. Control frames such as the control frame 508 aresometimes referred to herein as “SYNC frames” or “trigger frames”. In anembodiment, the AP utilizes sync frames 508 to indicate whether thecorresponding client devices are to acknowledge the MU DL transmission504 in an OFDMA ACK/BA or via a poll-based ACK procedure. For example,in an embodiment, if a respective SYNC frame 508 is present in the MU DLtransmission 504, this indicates to a corresponding client device thatthe client device is to transmit as part of an OFDMA ACK/BA; whereas ifa respective SYNC frame 508 is not present in the MU DL transmission504, this indicates to a corresponding client device that the clientdevice should acknowledge the MU DL transmission 504 via a poll-basedprocedure. In another embodiment, the AP includes information in eachsync frame 508 that indicates whether the corresponding client device isto acknowledge the MU DL transmission 504 in an OFDMA ACK/BA or via apoll-based ACK procedure.

In an embodiment, each SYNC frame 508 includes information thatindicates a length of the ACK/BA UL OFDMA transmission. For example, inan embodiment, each SYNC frame 508 indicates a number of orthogonalfrequency division multiplexing (OFDM) symbols in the ACK/BA UL OFDMAtransmission. As another example, in an embodiment, each SYNC frame 508indicates a modulation and coding scheme (MCS) and a bandwidth to beused by the corresponding client device in the ACK/BA UL OFDMAtransmission. For instance, in an embodiment, the MCS and bandwidth aredeterminative of the duration of the transmission.

In an embodiment, the communication frame 504 spans a bandwidth of aprimary channel (e.g., a primary 20 MHz channel) of the WLAN 10 andmultiple other secondary channels (e.g., 20 MHz channels) of the WLAN10, i.e., the communication frame 304 spans a bandwidth of a compositechannel comprising the primary channel and one or more secondarychannels.

In an embodiment, each client device to which a data transmission 506corresponds generates and transmits an ACK or BA portion as part of anUL OFDMA transmission 512 responsive to the communication frame 504. Forexample, in an embodiment, each client device to which a datatransmission 506 corresponds generates and transmits an ACK or BAportion 516 a defined time period (e.g., a SIFS or another suitable timeperiod) after the end of the communication frame 504. In an embodiment,each client device generates and transmits an ACK or BA portion 516 in arespective frequency block within a communication channel spanned by theMU DL transmission.

In the example of FIG. 5, each ACK or BA portion 516 has a same durationin time. Thus, in some embodiments, the AP determines the duration ofthe UL OFDMA transmission 512 and indicates to the client devices theduration of the UL OFDMA transmission 512. Then, each client devicegenerates the respective portion 516 to have the indicated duration. Forinstance, as described above, the AP includes information indicative ofthe duration of the UL OFDMA transmission 512 in each SYNC 508,according to an embodiment. As another example, the AP includesinformation indicative of the duration of the UL OFDMA transmission 512in a PHY preamble of the MU DL communication frame.

In some embodiments, the position and bandwidth within a MU DL OFDMAtransmission of data corresponding to a client device determines theposition and bandwidth within a MU UL ACK/BA transmission by the clientdevice. For example, in an embodiment, the client device generates andtransmits an ACK/BA at the same position and bandwidth as the positionand bandwidth within the MU DL OFDMA transmission of data correspondingto the client device. In some embodiments, the AP determines theposition and bandwidth within a MU UL ACK/BA transmission by the clientdevice, and informs the client device. For example, in an embodiment,the AP determines the position and bandwidth within a MU UL ACK/BAtransmission by the client device, and includes information indicatingthe position and bandwidth in the SYNC frame of the MU DL communicationframe, in a PHY preamble of the MU DL communication frame, etc. Theclient devices then utilize the information included in the MU DLcommunication frame to determine the positions and bandwidths within theMU UL ACK/BA that the client devices are to transmit.

In an embodiment, the SYNC frame 508 includes one or more bits thatindicate whether the client device should acknowledge the MU DLtransmission 504 in an OFDMA transmission. In an embodiment, the SYNCframe 508 includes one or more bits that indicate whether the clientdevice should acknowledge the MU DL transmission 504 using the samebandwidth, channel position, spatial stream(s), etc., of the portion ofthe MU DL transmission corresponding to the client device. In anembodiment, if the one or more bits do not indicate that the clientdevice should acknowledge the MU DL transmission 504 using the samebandwidth, channel position, spatial stream, etc., the AP may includeindications of the bandwidth, the channel position, the spatialstream(s), etc., to be utilized by the client device in the MU UL ACK/BAtransmission.

In some embodiments and/or scenarios, UL ACKs/BAs are incorporated in ULdata frames. FIG. 6A is a diagram of an example transmission sequence600 in a WLAN, such as the WLAN 10 of FIG. 1, according to anembodiment, in which an AP, such as the AP 14, transmits a DL OFDMAcommunication frame to multiple client stations, such as multiple onesof the client stations 25, during a TXOP 602.

The AP 14 generates and transmits a DL OFDMA communication frame 604, inan embodiment. In an embodiment, the communication frame 604 comprisesrespective data 606 for multiple client devices. In an illustrativeembodiment, the data 606 comprise respective A-MPDUs 606, where eachA-MPDU 606 includes a respective control frame 608 for controlling MU ULtransmissions.

In an embodiment, the communication frame 604 spans a bandwidth of aprimary channel (e.g., a primary 20 MHz channel) of the WLAN 10 andmultiple other secondary channels (e.g., 20 MHz channels) of the WLAN10, i.e., the communication frame 604 spans a bandwidth of a compositechannel comprising the primary channel and one or more secondarychannels.

In an embodiment, each client device to which a data transmission 606corresponds generates and transmits data as part of an UL OFDMAtransmission 612 responsive to the communication frame 604. For example,in an embodiment, each client device to which a data transmission 606corresponds generates and transmits a portion 616 a defined time period(e.g., a SIFS or another suitable time period) after the end of thecommunication frame 604. In an embodiment, each client device generatesand transmits a data portion 616 in a respective frequency block withina communication channel spanned by the MU DL transmission. In anembodiment, each portion 616 is a respective quality of service(QoS)+contention free (CF)-ACK (QoS+CF-ACK) frame. Each QoS+CF-ACK frame616 serves as a respective acknowledgment of the MU DL communicationframe 604 from the respective client devices.

In an embodiment, the AP generates and transmits a DL OFDMA transmission624 acknowledging the MU UL transmission 612.

FIG. 6B is a diagram of an example transmission sequence 650 in a WLAN,such as the WLAN 10 of FIG. 1, according to an embodiment, in which anAP, such as the AP 14, transmits a DL OFDMA communication frame tomultiple client stations, such as multiple ones of the client stations25, during a TXOP 652.

The AP 14 generates and transmits a DL OFDMA communication frame 654, inan embodiment. In an embodiment, the communication frame 654 comprisesrespective data 656 for multiple client devices. In an illustrativeembodiment, the data 656 comprise respective A-MPDUs 656, where eachA-MPDU 656 includes a respective control frame 658 for controlling MU ULtransmissions.

In an embodiment, the communication frame 654 spans a bandwidth of aprimary channel (e.g., a primary 20 MHz channel) of the WLAN 10 andmultiple other secondary channels (e.g., 20 MHz channels) of the WLAN10, i.e., the communication frame 654 spans a bandwidth of a compositechannel comprising the primary channel and one or more secondarychannels.

In an embodiment, each client device to which a data transmission 656corresponds generates and transmits data as part of an UL OFDMAtransmission 662 responsive to the communication frame 654. For example,in an embodiment, each client device to which a data transmission 656corresponds generates and transmits a portion 668 a defined time period(e.g., a SIFS or another suitable time period) after the end of thecommunication frame 654. In an embodiment, each client device generatesand transmits a data portion 668 in a respective frequency block withina communication channel spanned by the MU DL transmission. In anembodiment, each portion 668 is a respective MPDU frame with a BA 674.In an embodiment, each portion 668 is a respective A-MPDU with a datafirst MPDU having data and a second MPDU corresponding to a BA frame.

In an embodiment, the AP generates and transmits a DL OFDMA transmission678 acknowledging the MU UL transmission 662.

FIG. 7 is a diagram of an example A-MPDU 700 that may be utilized by theAP in MU DL transmissions and/or by a client device in MU ULtransmissions, according to some embodiments. Thus, in some embodiments,the network interface device 16 (FIG. 1) (e.g., the MAC processing unit18) is configured to generate and transmit A-MPDUs such as the A-MPDU700. Similarly, in some embodiments, the network interface device 27(FIG. 1) (e.g., the MAC processing unit 28) is configured to generateand transmit A-MPDUs such as the A-MPDU 700.

The A-MPDU 700 is included in an OFDMA PPDU for transmission. Thus, insome embodiments, the network interface device 16 (FIG. 1) (e.g., thePHY processing unit 20) is configured to generate and transmit a PPDUincluding an A-MPDU such as the A-MPDU 700. Similarly, in someembodiments, the network interface device 27 (FIG. 1) (e.g., the PHYprocessing unit 29) is configured to generate and transmit a PPDUincluding an A-MPDU such as the A-MPDU 700.

The A-MPDU 700 includes a control frame portion 704 and a data portion708. In some embodiments, the control frame portion 704 comprises one ormore A-MPDU subframes. In some embodiments, the data portion 708comprises one or more A-MPDU subframes. In an embodiment, the dataportion 708 includes only one A-MPDU subframe, and the A-MPDU 700 issometimes referred to as a “HEW single data frame”. In some embodiments,a communication device that correctly receives a HEW single data frameacknowledges the HEW single data frame with an ACK, a QoS+CF-ACK frame,etc. In some embodiments, a communication device that correctly receivesa HEW single data frame acknowledges the HEW single data frame with aBA.

In an embodiment, the control frame portion 704 is at a beginning (intime) of the A-MPDU 700, and the data portion 708 is at an end (in time)of the A-MPDU 700, as illustrated in FIG. 7. In other embodiments,however, the control frame portion 704 is at an end (in time) of theA-MPDU 700, and the data portion 708 is at a beginning (in time) of theA-MPDU 700.

In various embodiments and/or scenarios, the control frame portion 704includes an ACK, a BA, a BAR, a SYNC, etc. Thus, in some embodiments, atleast some of the A-MPDUs illustrated in FIGS. 2-6 have a format thesame as or similar to the example A-MPDU 700. In other embodiments,however, at least some of the A-MPDUs illustrated in FIGS. 2-6 have aformat different than the example A-MPDU 700.

In an embodiment, each A-MPDU subframe in the A-MPDU 700 includes anMPDU delimiter field, and each MPDU delimiter field includes an end offrame (EOF) flag. For example, the control frame portion 704 includes anA-MPDU subframe 720. The A-MPDU subframe 720 includes a MPDU delimiterfield 724 having an EOF flag 740. In an embodiment, the EOF flag 740 isset to a value to indicate that the A-MPDU subframe 720 is not the lastsubframe in the A-MPDU 700 (e.g., the EOF flag 740 is set to zero). Inan embodiment, all EOF flags corresponding to all A-MPDU subframes inthe control frame portion 704 are set to a value to indicate that theA-MPDU subframes in the control frame portion 704 are not the lastsubframe in the A-MPDU 700 (e.g., the EOF flags are set to zero).

The A-MPDU subframe 760 includes a MPDU delimiter field 764 having anEOF flag 780. In an embodiment, the EOF flag 780 is set to a value toindicate that the A-MPDU subframe 760 is the last subframe in the A-MPDU700 (e.g., the EOF flag 780 is set to one). In an embodiment, EOF flagsof other A-MPDU subframes in the data portion 708 prior (in time) to theA-MPDU subframe 760 (if any) are set to a value to indicate that thoseA-MPDU subframes in the data portion 708 are not the last subframe inthe A-MPDU 700 (e.g., the EOF flags are set to zero).

FIGS. 8A and 8B are diagrams of example A-MPDUs that may be utilized bythe AP in MU DL transmissions, according to some embodiments. Thus, insome embodiments, the network interface device 16 (FIG. 1) (e.g., theMAC processing unit 18) is configured to generate and transmit A-MPDUssuch as the A-MPDU 800 and/or the A-MPDU 804.

The A-MPDU 800/850 is included in an OFDMA PPDU for transmission. Thus,in some embodiments, the network interface device 16 (FIG. 1) (e.g., thePHY processing unit 20) is configured to generate and transmit a PPDUincluding an A-MPDU such as the A-MPDU 800 and/or the A-MPDU 804.

Referring now to FIG. 8A, the A-MPDU 800 includes an A-MPDU subframe 804corresponding to a SYNC, and an A-MPDU subframe 808 corresponding todata. In an embodiment, the A-MPDU 800 is an example of a HEW singledata frame. In some embodiments, a communication device that correctlyreceives a HEW single data frame acknowledges the HEW single data framewith an ACK, a QoS+CF-ACK frame, etc. In some embodiments, acommunication device that correctly receives a HEW single data frameacknowledges the HEW single data frame with a BA.

In an embodiment, the A-MPDU subframe 804 is at a beginning (in time) ofthe A-MPDU 800, and the A-MPDU subframe 808 is at an end (in time) ofthe A-MPDU 800, as illustrated in FIG. 8A.

In some embodiments, at least some of the A-MPDUs illustrated in FIGS.2-6 transmitted by the AP in a MU DL transmission have a format the sameas or similar to the example A-MPDU 800. In other embodiments, however,at least some of the A-MPDUs illustrated in FIGS. 2-6 transmitted by theAP in a MU DL transmission have a format different than the exampleA-MPDU 800.

In an embodiment, the A-MPDU subframe 804 includes an MPDU delimiterfield having an EOF flag set to a value to indicate that the A-MPDUsubframe 804 is not the last subframe in the A-MPDU 800 (e.g., the EOFflag is set to zero). The A-MPDU subframe 808 includes a MPDU delimiterfield having an EOF flag set to a value to indicate that the A-MPDUsubframe 808 is the last subframe in the A-MPDU 800 (e.g., the EOF flagis set to one).

Referring now to FIG. 8B, the A-MPDU 850 includes an A-MPDU subframe 854corresponding to data, and an A-MPDU subframe 858 corresponding to SYNC.In an embodiment, the A-MPDU 850 is an example of a HEW single dataframe. In some embodiments, a communication device that correctlyreceives a HEW single data frame acknowledges the HEW single data framewith an ACK, a QoS+CF-ACK frame, etc. In some embodiments, acommunication device that correctly receives a HEW single data frameacknowledges the HEW single data frame with a BA.

In an embodiment, the A-MPDU subframe 854 is at a beginning (in time) ofthe A-MPDU 850, and the A-MPDU subframe 858 is at an end (in time) ofthe A-MPDU 850, as illustrated in FIG. 8B.

In some embodiments, at least some of the A-MPDUs illustrated in FIGS.2-6 transmitted by the AP in a MU DL transmission have a format the sameas or similar to the example A-MPDU 850. In other embodiments, however,at least some of the A-MPDUs illustrated in FIGS. 2-6 transmitted by theAP in a MU DL transmission have a format different than the exampleA-MPDU 850.

In an embodiment, the A-MPDU subframe 854 includes an MPDU delimiterfield having an EOF flag set to a value to indicate that the A-MPDUsubframe 854 is not the last subframe in the A-MPDU 850 (e.g., the EOFflag is set to zero). In another embodiment, the A-MPDU subframe 854includes an MPDU delimiter field having an EOF flag set to a value toindicate that the A-MPDU subframe 854 is the last subframe in the A-MPDU850 (e.g., the EOF flag is set to one). The A-MPDU subframe 858 includesa MPDU delimiter field having an EOF flag set to a value to indicatethat the A-MPDU subframe 858 is the last subframe in the A-MPDU 850(e.g., the EOF flag is set to one).

In other embodiments, more than one A-MPDU subframe corresponding todata is included in the A-MPDU 800 and/or the A-MPDU 850. For example,in some embodiments, with respect to the example A-MPDU 800, furtherA-MPDU subframes corresponding to data are included after (in time) theA-MPDU subframe 804 and prior to (in time) the A-MPDU subframe 808, andsuch further A-MPDU subframes corresponding to data each have an EOFflag set to a value to indicate that the A-MPDU subframe is not the lastsubframe in the A-MPDU 800 (e.g., the EOF flag is set to zero). Asanother example, in some embodiments, with respect to the example A-MPDU850, further A-MPDU subframes corresponding to data are included priorto (in time) the A-MPDU subframe 854, and such further A-MPDU subframescorresponding to data each have an EOF flag set to a value to indicatethat the A-MPDU subframe is not the last subframe in the A-MPDU 850(e.g., the EOF flag is set to zero). In an embodiment, the EOF flag ofthe A-MPDU subframe 854 includes is set to a value to indicate that theA-MPDU subframe 854 is the last subframe in the A-MPDU 850 (e.g., theEOF flag is set to one).

In some embodiments, a MU DL transmission may utilize both OFDMA andMU-MIMO. In some embodiments, the AP may determine whether clientdevices are to acknowledge an MU DL transmission that utilizes bothOFDMA and MU-MIMO with i) poll-based acknowledgments or ii) OFDMAacknowledgments.

For example, FIGS. 9A and 9B illustrate examples of MU DL transmissionthat utilize both OFDMA and MU-MIMO. In FIG. 9A, the AP has determinedthat client devices are to acknowledge an MU DL transmission thatutilizes both OFDMA and MU-MIMO with poll-based acknowledgments. Thus,in an embodiment, the MU DL transmission does not include SYNC frames toindicate to the client devices that the client devices are toacknowledge the MU DL transmission with poll-based acknowledgments. Onthe other hand, in FIG. 9B, the AP has determined that client devicesare to acknowledge an MU DL transmission that utilizes both OFDMA andMU-MIMO with an OFDMA acknowledgment. Thus, in an embodiment, the MU DLtransmission includes SYNC frames i) to indicate to the client devicesthat the client devices are to acknowledge the MU DL transmission withan OFDMA acknowledgment, and ii) to prompt the client devices totransmit the OFDMA acknowledgment.

FIG. 9A is a diagram of an example transmission sequence 900 in a WLAN,such as the WLAN 10 of FIG. 1, according to an embodiment, in which anAP, such as the AP 14, transmits a DL OFDMA communication frame tomultiple client stations, such as multiple ones of the client stations25, during a TXOP 902.

The AP 14 generates and transmits a DL OFDMA communication frame 904, inan embodiment. In an embodiment, the communication frame 904 comprisesrespective data 906 for multiple client devices. In an illustrativeembodiment, the data 906 comprise respective A-MPDUs 906. In anembodiment, the communication frame 904 spans a bandwidth of a primarychannel (e.g., a primary 20 MHz channel) of the WLAN 10 and multipleother secondary channels (e.g., 20 MHz channels) of the WLAN 10, i.e.,the communication frame 904 spans a bandwidth of a composite channelcomprising the primary channel and one or more secondary channels.

In an embodiment, the different data 906 correspond to differentpositions (in terms of frequency) within the communication frame 904,where each position is indicated by an index. For example, in anembodiment, the index starts at the lowest (in frequency) portion of theaggregate channel and increases as frequency increases. In anotherembodiment, the index starts at the highest (in frequency) portion ofthe aggregate channel and decreases as frequency decreases. Referring tothe example illustrated in FIG. 9A, in an embodiment, A-MPDU 906-1corresponds to a first position, A-MPDU 906-2 corresponds to a secondposition, etc. In some embodiments and/or scenarios, each positioncorresponds to a 20 MHz channel. In other embodiments and/or scenarios,each position may correspond to a single 20 MHz channel or a compositeof multiple 20 MHz channels. In other embodiments and/or scenarios, eachposition may correspond to a single 20 MHz channel, a composite ofmultiple 20 MHz channels, or different portions of a single 20 MHzchannel.

In an embodiment, the A-MPDU 906-2 is a MU-MIMO transmission to STA1 andSTA2. In an embodiment, the A-MPDU 906-2 is transmitted in a compositechannel composing multiple 20 MHz channels.

Because the MU DL PPDU 904 does not include SYNCs, the client devices(e.g., STA0-STA3) determine that the client devices are to acknowledgethe MU DL PPDU 904 using poll-based acknowledgments, according to anembodiment.

In an embodiment, the client device corresponding to the datatransmission in the first position (e.g., STA0 corresponding to A-MPDU906-1) generates and transmits an ACK/BA frame to the AP via an ULchannel responsive to the communication frame 904. For example, in anembodiment, the client device corresponding to the data transmission inthe first position generates and transmits an ACK frame or BA frame adefined time period (e.g., a SIFS or another suitable time period) afterthe end of the communication frame 904. In an embodiment, the clientdevice corresponding to the data transmission in the first positiongenerates an ACK frame or BA frame that spans a 20 MHz channel,duplicates the ACK/BA frame in one or more other 20 MHz channels, andsimultaneously transmits the ACK/BA and the duplicates of the ACK/BA.For instance, in the example of FIG. 9A, STA0 transmits multipleinstances of a BA frame 908 in multiple 20 MHz channels corresponding tothe bandwidth of the communication frame 204. In some embodiments, theACK/BA is formatted according to the HEW protocol. In some embodiments,the ACK/BA is formatted according to a legacy protocol.

After receiving the ACK/BA 908, the AP generates and transmits a BARframe to prompt another client device (e.g., STA1) to transmit a BA toacknowledge the DL transmission 904. In an embodiment, the AP generatesa BAR frame that spans a 20 MHz channel, duplicates the BAR frame in oneor more other 20 MHz channels, and simultaneously transmits the BARframe and the duplicates of the BAR frame. For instance, in the exampleof FIG. 9A, the AP transmits multiple instances of a BAR frame 912 inmultiple 20 MHz channels corresponding to the bandwidth of thecommunication frame 904. In response to the BAR frame 912, thecorresponding client device (e.g., STA1) generates an ACK frame or BAframe that spans a 20 MHz channel, duplicates the ACK/BA frame in one ormore other 20 MHz channels, and simultaneously transmits the ACK/BA andthe duplicates of the ACK/BA. For instance, in the example of FIG. 9A,STA1 transmits multiple instances of a BA frame 916 in multiple 20 MHzchannels corresponding to the bandwidth of the communication frame 904.

After receiving the ACK/BA 916, the AP generates and transmits a BARframe to prompt another client device (e.g., STA2) to transmit an ACK/BAto acknowledge the DL transmission 904. In an embodiment, the APgenerates a BAR frame that spans a 20 MHz channel, duplicates the BARframe in one or more other 20 MHz channels, and simultaneously transmitsthe BAR frame and the duplicates of the BAR frame. For instance, in theexample of FIG. 9A, the AP transmits multiple instances of a BAR frame920 in multiple 20 MHz channels corresponding to the bandwidth of thecommunication frame 904. In response to the BAR frame 920, thecorresponding client device (e.g., STA2) generates an ACK frame or BAframe that spans a 20 MHz channel, duplicates the ACK/BA frame in one ormore other 20 MHz channels, and simultaneously transmits the ACK/BA andthe duplicates of the ACK/BA. For instance, in the example of FIG. 9A,STA2 transmits multiple instances of a BA frame 924 in multiple 20 MHzchannels corresponding to the bandwidth of the communication frame 904.

After receiving the ACK/BA 924, the AP generates and transmits a BARframe to prompt a last client device (e.g., STA3) to transmit an ACK/BAto acknowledge the DL transmission 904. In an embodiment, the APgenerates a BAR frame that spans a 20 MHz channel, duplicates the BARframe in one or more other 20 MHz channels, and simultaneously transmitsthe BAR frame and the duplicates of the BAR frame. For instance, in theexample of FIG. 9A, the AP transmits multiple instances of a BAR frame928 in multiple 20 MHz channels corresponding to the bandwidth of thecommunication frame 904. In response to the BAR frame 928, thecorresponding client device (e.g., STA3) generates an ACK frame or BAframe that spans a 20 MHz channel, duplicates the ACK/BA frame in one ormore other 20 MHz channels, and simultaneously transmits the ACK/BA andthe duplicates of the ACK/BA. For instance, in the example of FIG. 9A,STA3 transmits multiple instances of a BA frame 932 in multiple 20 MHzchannels corresponding to the bandwidth of the communication frame 904.

In some embodiments, client devices transmit ACKs/BAs for a DLOFDMA/MU-MIMO frame sequentially in a manner similar to FIG. 9A, butwithout being polled by the AP. For example, in an embodiment, the APassigns STAs to groups and broadcasts (or multicasts) an indication ofgroup membership by listing association IDs (AIDs) of STAs within thegroup. In such embodiments, the order of AIDs in the group membershipbroadcast/multicast indicate an order in which client devices shouldtransmit ACKs/BAs of a DL OFDMA/MU-MIMO frame.

In some embodiments in which a DL OFDMA frame also includes a MU-MIMOtransmission (e.g., A-MPDU 906-2 in FIG. 9A and A-MPDU 956-3 in FIG.9B), the order of AIDs in the group membership broadcast/multicastindicate positions, in frequency, of transmissions within an OFDMAACK/BA. For instance, in the illustrative example of FIG. 9B, thepositions, in frequency, of BA 968-2 and BA 968-3 are determined basedon the order of AIDs in the group membership broadcast/multicast, in anembodiment.

In some embodiments in which a DL OFDMA frame includes a MU-MIMOtransmission spanning only 20 MHz, recipients of the MU-MIMOtransmission acknowledge the MU-MIMO transmission with an UL OFDMAtransmission in which different client devices transmit in differentgroups of OFDM tones (e.g., groups of 26 tones) within the 20 MHzchannel. Determining which client devices transmit on which groups ofOFDM tones utilize techniques such as described herein, in variousembodiments.

In some embodiments in which a DL OFDMA frame includes a MU-MIMOtransmission, recipients of the MU-MIMO transmission acknowledge theMU-MIMO transmission with an UL MU-MIMO transmission in which differentclient devices transmit via different spatial streams. In someembodiments, the AP may assign different client devices to differentspatial streams and inform the client devices of the assignments usingtechniques such as described herein. In some embodiments, client devicesmay determine the spatial streams to use to acknowledge the DL MU-MIMOtransmission as the same spatial streams used by the AP in the DLMU-MIMO transmission. In some embodiments, client devices may determinethe spatial streams to use to acknowledge the DL MU-MIMO transmissionbased on the order of AIDs in the group membership broadcast/multicast.

FIG. 9B is a diagram of an example transmission sequence 950 in a WLAN,such as the WLAN 10 of FIG. 1, according to an embodiment, in which anAP, such as the AP 14, transmits a DL OFDMA communication frame tomultiple client stations, such as multiple ones of the client stations25, during a TXOP 952.

The AP 14 generates and transmits a DL OFDMA communication frame 954, inan embodiment. In an embodiment, the communication frame 544 comprisesrespective data 956 for multiple client devices. In an illustrativeembodiment, the data 956 comprise respective A-MPDUs 956, where eachA-MPDU 956 includes a respective control frame 960 for controlling MU ULtransmissions. For example, in an embodiment, the AP has determined thatclient devices are to respond with an OFDMA acknowledgment, and thus theAP includes SYNCs 960 in the MU DL transmission 954. Because the MU DLPPDU 954 includes SYNCs 960, the client devices (e.g., STA0-STA3)determine that the client devices are to acknowledge the MU DL PPDU 954using an OFDMA acknowledgment, according to an embodiment. Additionally,in an embodiment, the SYNCs 960 prompt the client devices (e.g.,STA0-STA3) to transmit the OFDMA acknowledgment.

In an embodiment, each SYNC frame 960 includes information thatindicates a length of the ACK/BA UL OFDMA transmission. For example, inan embodiment, each SYNC frame 960 indicates a number of OFDM symbols inthe ACK/BA UL OFDMA transmission. As another example, in an embodiment,each SYNC frame 960 indicates an MCS and a bandwidth to be used by thecorresponding client device in the ACK/BA UL OFDMA transmission. Forinstance, in an embodiment, the MCS and bandwidth are determinative ofthe duration of the transmission.

In an embodiment, the communication frame 954 spans a bandwidth of aprimary channel (e.g., a primary 20 MHz channel) of the WLAN 10 andmultiple other secondary channels (e.g., 20 MHz channels) of the WLAN10, i.e., the communication frame 954 spans a bandwidth of a compositechannel comprising the primary channel and one or more secondarychannels.

In an embodiment, each client device to which a data transmission 956corresponds generates and transmits an ACK or BA portion as part of anUL OFDMA transmission 964 responsive to the communication frame 954. Forexample, in an embodiment, each client device to which a datatransmission 956 corresponds generates and transmits an ACK or BAportion 968 a defined time period (e.g., a SIFS or another suitable timeperiod) after the end of the communication frame 954. In an embodiment,each client device generates and transmits an ACK or BA portion 968 in arespective frequency block within a communication channel spanned by theMU DL transmission.

In the example of FIG. 9B, each ACK or BA portion 968 has a sameduration in time. Thus, in some embodiments, the AP determines theduration of the UL OFDMA transmission 964 and indicates to the clientdevices the duration of the UL OFDMA transmission 964. Then, each clientdevice generates the respective portion 968 to have the indicatedduration. For instance, as described above, the AP includes informationindicative of the duration of the UL OFDMA transmission 964 in each SYNC960, according to an embodiment. As another example, the AP includesinformation indicative of the duration of the UL OFDMA transmission 964in a PHY preamble of the MU DL communication frame.

In some embodiments, the AP determines the position and bandwidth withina MU UL ACK/BA transmission by the client device, and informs the clientdevice. For example, in an embodiment, the AP determines the positionand bandwidth within a MU UL ACK/BA transmission by the client device,and includes information indicating the position and bandwidth in theSYNC frame of the MU DL communication frame, in a PHY preamble of the MUDL communication frame, etc. The client devices then utilize theinformation included in the MU DL communication frame to determine thepositions and bandwidths within the MU UL ACK/BA that the client devicesare to transmit.

In an embodiment, the SYNC frame 960 includes one or more bits thatindicate whether the client device should acknowledge the MU DLtransmission 954 in an OFDMA transmission. In an embodiment, the AP mayinclude indications of the bandwidth, the channel position, the spatialstream(s), etc., to be utilized by the client device in the MU UL ACK/BAtransmission 964.

In various embodiments, each data transmission 956 has a format the sameas or similar to the A-MPDU format 700 (FIG. 7), the A-MPDU format 800(FIG. 8A), the A-MPDU format 850 (FIG. 8B), or another suitable format.

In some embodiments, a client device is not able to transmit across afull composite channel via which the MU DL communication frame istransmitted. As an illustrative example, an AP may be capable oftransmitting at a cumulative bandwidth of 80 MHz, 160 MHz, 320, MHz,etc., in various embodiments, but a client device may have a maximumtransmission bandwidth capability of only 40 MHz.

FIG. 10 is a diagram of an example transmission sequence 1000 in a WLAN,such as the WLAN 10 of FIG. 1, according to an embodiment, in which anAP, such as the AP 14, transmits a DL OFDMA communication frame tomultiple client stations, such as multiple ones of the client stations25, during a TXOP 1002.

The AP 14 generates and transmits a DL OFDMA communication frame 1004,in an embodiment. In an embodiment, the communication frame 1004comprises respective data 1006 for multiple client devices. In anillustrative embodiment, the DL OFDMA communication frame 1004 spans acumulative bandwidth of 160 MHz. In an embodiment, some client devices(e.g., STA0 and STA2) are capable of transmitting at a cumulativebandwidth of 160 MHz, but other client devices (e.g., STA1 and STA3)have a maximum transmission bandwidth capability of only 80 MHz.

In an embodiment, client devices capable of transmitting at the samebandwidth as the DL OFDMA communication frame 1004 duplicate their BAsto span the entire bandwidth of the DL OFDMA communication frame 1004,whereas client devices not capable of transmitting at the same bandwidthas the DL OFDMA communication frame 1004 duplicate their BAs to span theonly a portion of the bandwidth of the DL OFDMA communication frame1004. For instance, in the example illustrated in FIG. 10, STA0transmits BAs 1008 spanning the entire bandwidth of the DL OFDMAcommunication frame 1004, and STA2 transmits BAs 1024 spanning theentire bandwidth of the DL OFDMA communication frame 1004, according toan embodiment. On the other hand, STA1 transmits BAs 1016 spanning onlya portion of the bandwidth of the DL OFDMA communication frame 1004, andSTA3 transmits BAs 1032 spanning only the portion of the bandwidth ofthe DL OFDMA communication frame 1004, according to an embodiment. In anembodiment, the bandwidth portion of the BA transmission by the clientdevice is chosen to span at least the bandwidth portion of the datatransmission 1006 corresponding to the client device. For instance, inthe example of FIG. 10, the bandwidth spanned by BAs 1016 completelyoverlaps the bandwidth of the data portion 1006-1 in the MU DLtransmission 1004. Similarly, the bandwidth spanned by BAs 1032completely overlaps the bandwidth of the data portion 1006-3 in the MUDL transmission 1004.

In an embodiment, to mitigate hidden node problems, the AP transmitsBARs across the entire bandwidth spanned by the MU DL transmission 1004regardless of the bandwidth capability of the client devices. Forinstance, in the example of FIG. 10, the AP transmits BARs 1012 spanningthe entire bandwidth of the MU DL transmission 1004 even though STA1 isnot capable of transmitting BAs 1016 across the entire bandwidth of theMU DL transmission 1004. Similarly, the AP transmits BARs 1028 spanningthe entire bandwidth of the MU DL transmission 1004 even though STA3 isnot capable of transmitting BAs 1032 across the entire bandwidth of theMU DL transmission 1004.

As discussed above, in some embodiments, not all client devices arecapable of transmitting an acknowledgment via OFDMA. Thus, in someembodiments, a combination of OFDMA and poll-based acknowledgments areutilized to acknowledge a single MU DL transmission.

FIG. 11 is a diagram of an example transmission sequence 1100 in a WLAN,such as the WLAN 10 of FIG. 1, according to an embodiment, in which anAP, such as the AP 14, transmits a DL OFDMA communication frame tomultiple client stations, such as multiple ones of the client stations25, during a TXOP 1102.

The AP 14 generates and transmits a DL OFDMA communication frame 1104,in an embodiment. In an embodiment, the communication frame 1104comprises respective data 1106 for multiple client devices. In anillustrative embodiment, the data 1106 comprise respective A-MPDUs 1106.In an embodiment, the communication frame 1104 spans a bandwidth of aprimary channel (e.g., a primary 20 MHz channel) of the WLAN 10 andmultiple other secondary channels (e.g., 20 MHz channels) of the WLAN10, i.e., the communication frame 1104 spans a bandwidth of a compositechannel comprising the primary channel and one or more secondarychannels.

In an embodiment, some of the client devices to which data transmissions1106 correspond generates and transmit respective ACK or BA portion aspart of an UL OFDMA transmission 1108 responsive to the communicationframe 1104. For example, in an embodiment, some client devices to whichdata transmissions 1106 corresponds generate and transmit respective ACKor BA portions 1112 a defined time period (e.g., a SIFS or anothersuitable time period) after the end of the communication frame 1104. Inan embodiment, some client devices generate and transmit respective ACKor BA portions 1112 in respective frequency blocks within acommunication channel spanned by the MU DL transmission. On the otherhand, some client devices to which data transmissions 1106 correspondsgenerate and transmit respective non-OFDMA transmissions a defined timeperiod (e.g., a SIFS or another suitable time period) after the end ofthe communication frame 1104. In an embodiment, some client devicesgenerate and transmit respective non-OFDMA transmissions 1116 inrespective frequency blocks within a communication channel spanned bythe MU DL transmission.

The non-OFDMA transmissions 1116 may comprise one of or any suitablecombination of two or more of padding, padding with an A-MPDU delimiter,a QoS Null frame, a clear-to-send-to-self (CTS-to-self) frame, etc. Inan embodiment, a suitable non-OFDMA transmission 1116 is generated in a20 MHz channel and then duplicated to one or more other 20 MHz channels,if needed.

In the example of FIG. 11, STA0-STA2 participate in the OFDMAtransmission 1108, while STA3 transmits a suitable non-OFDMAtransmission 1116. STA0 generates and transmits portions 1112-1. STA1generates and transmits portion 1112-2. STA2 generates and transmitsportion 1112-3. STA3 generates a non-OFDMA frame 1116, duplicates theframe 1116, and transmits the frame 1116 and the duplicate of the frame1116.

After receiving the UL transmission 1116, the AP determines that STA3 isnot capable of transmitting as part of the OFDMA ACK transmission 1108.In response, the AP generates and transmits a BAR frame to prompt STA3to transmit a BA to acknowledge the DL transmission 1104. In anembodiment, the AP generates a BAR frame that spans a 20 MHz channel,duplicates the BAR frame in one or more other 20 MHz channels, andsimultaneously transmits the BAR frame and the duplicates of the BARframe. For instance, in the example of FIG. 11, the AP transmitsmultiple instances of a BAR frame 1120 in multiple 20 MHz channelscorresponding to the bandwidth of the communication frame 1104. Inresponse to the BAR frame 1120, STA3 generates an ACK frame or BA framethat spans a 20 MHz channel, duplicates the ACK/BA frame in one or moreother 20 MHz channels, and simultaneously transmits the ACK/BA and theduplicates of the ACK/BA. For instance, in the example of FIG. 11, STA3transmits multiple instances of a BA frame 1124 in multiple 20 MHzchannels that completely overlap with the bandwidth spanned by the DLtransmission 1006-4.

As discussed above, in some embodiments, ACK/BA transmissions in an ULOFDMA are permitted to have different time durations. In otherembodiments, however, ACK/BA transmissions in an UL OFDMA should havethe same time duration or substantially the same duration (e.g., differby no more than 10%, 5%, 2%, 1%, etc., according to variousembodiments).

In some embodiments in which ACK/BA transmissions in an UL OFDMA shouldhave the same time duration or substantially the same duration, the APprovides information indicating a duration (in time) of the ACK/BAtransmissions to the client devices so that the client devices cangenerate ACK/BA transmissions of the indicated duration.

In an embodiment, the AP determines the ACK/BA duration for each clientdevice using any suitable combination of two or more of the following: aknown length of the MPDU corresponding to the ACK/BA to be transmitted,an MCS for the ACK/BA, a candidate rate for the ACK/BA, a candidatebandwidth for the ACK/BA, etc. In an embodiment, the AP selects the MCSfrom a set of candidate MCSs. In an embodiment, the AP selects themaximum MCS from the set of candidate MCSs. In an embodiment, the set ofcandidate MCSs corresponds to MCSs that are common to receiving MCSs ofthe AP and transmitting MCSs of the client device. In an embodiment, theset of candidate MCSs includes a basic MCS set of a basic service set(BSSBasicMCSSet) of a BSS served by the AP 14. In an embodiment, the setof candidate MCSs includes mandatory MCSs supported by the PHYprocessing unit 20 of the AP 14, in an embodiment. In an embodiment,when the BSSBasicMCSSet is empty or idle, the set of candidate MCSs isthe set of mandatory MCSs supported by the PHY processing unit 20 of theAP 14, in an embodiment.

After the AP determines the ACK/BA duration for each client device, theAP selects the maximum ACK/BA duration from the determined ACK/BAdurations for the client devices as the duration of the OFDMA ACK/BA tobe used in the uplink. Then, the AP transmits an indication of theselected ACK/BA duration to the client devices. For example, theindication of the selected ACK/BA duration is included in a SYNC in theMU DL PPDU as discussed above, in some embodiments. As another example,the indication of the selected ACK/BA duration is included in PHYpreamble of the MU DL PPDU, in some embodiments.

In an embodiment, each client device uses the indication of the selectedACK/BA duration to select an MCS and adds padding (if necessary) so thata duration of the ACK/BA generated by the client device is substantiallythe same as the selected ACK/BA duration.

In one embodiment, all client device transmissions constituting an OFDMAacknowledgment are transmitted via a single spatial stream. In anotherembodiment, each client device uses the smaller of i) the number oftransmit spatial streams capacity of the client device, and ii) thespatial stream(s) utilized to transmit to the client device in the MU DLtransmission that is being acknowledged.

In one embodiment, each client device transmits for the OFDMAacknowledgment on the same OFDM subchannels utilized for the clientdevice in the MU DL PPDU. In another embodiment, the AP determines theOFDM subchannels to be used by each client device for the OFDMAacknowledgment, and the AP includes indications of determined OFDMsubchannels in a SYNC frame, in a PHY preamble of the MU DL PPDU, inanother suitable location within the MU DL PPDU, etc.

As discussed above, in some embodiments, the AP may include, in a PHYheader of a MU DL PPDU, information that provides information to clientdevices to indicate to the client devices how to generate anOFDMA/MU-MIMO acknowledgment for the MU DL PPDU. FIG. 12 is a diagram ofan example MU DL PPDU 1200 (or a portion thereof) that may be utilizedby the AP, according to some embodiments. In an embodiment, the AP 14 isconfigured to generate and transmit to multiple client stations usingOFDMA and/or MU-MIMO, according to an embodiment. The data unit 1200conforms to the HE communication protocol and occupies a suitablebandwidth such as 20 MHz, 40 MHz, 80 MHz, 160 MHz, 320 MHz, 640 MHz, forexample, or other suitable bandwidths, in other embodiments.

The data unit 1200 includes a PHY preamble 1202 having a legacy preambleportion 1203 and an HE preamble portion 1204. The HE PHY preamble 1202includes a legacy short training field (L-STF) 1205, a legacy longtraining field (L-LTF) 1210, an L-SIG 1215, a first HE signal field(HE-SIG-A) 1220, a second HE signal field (HE-SIG-B) 1222, an HE shorttraining field (HE-STF) 1225, and M HE long training fields (HE-LTFs)1230, where M is an integer. In some embodiments and/or scenarios, thePHY preamble 1202 omits one or more of the fields 1205-1235. In someembodiments, the preamble 1202 includes additional fields notillustrated in FIG. 12. For example, in some embodiments, the PHYpreamble 1202 includes a third HE signal field (HE-SIG-C) after theHE-LTFs 1230 or at another suitable location in the preamble 1202.

The data unit 1200 also includes a data portion 1240.

Each of the L-STF 1205, the L-LTF 1210, the L-SIG 1215, the HE-SIG-A1220, the HE-SIG-B 1222, the HE-STF 1225, and the M HE-LTFs 1230comprises an integer number of one or more OFDM symbols. As merely anexample, in an embodiment, the HE-SIG-A 1220 comprises only two OFDMsymbols, and the HE-SIG-B 1222 comprises only one OFDM symbol. As merelyanother example, in another embodiment, the HE-SIG-A 1220 comprises onlyone OFDM symbol, and the HE-SIG-B 1222 comprises only two OFDM symbols.In other embodiments, the HE-SIG-A 1220 and the HE-SIG-B 1222 comprisesother suitable numbers of OFDM symbols.

In some embodiments, the data unit 1200 occupies a cumulative bandwidthgreater than 20 MHz, and each of the L-STF 1205, the L-LTF 1210, theL-SIG 1215, the HE-SIG-A 1220, and the HE-SIG-B 1222 is repeated over acorresponding number of 20 MHz sub-bands of the whole bandwidth of thedata unit, in an embodiment. For example, in an embodiment, the dataunit occupies an 80 MHz bandwidth and, accordingly, includes four ofeach of the L-STF 1205, the L-LTF 1210, the L-SIG 1215, the HE-SIG-A1220, and the HE-SIG-B 1235. In some embodiments, the modulation ofdifferent 20 MHz sub-bands signals is rotated by different angles. Forexample, in one embodiment, all OFDM tones within a first subband arerotated 0-degrees, all OFDM tones within a second subband is rotated90-degrees, a third sub-band is rotated 180-degrees, and a fourthsub-band is rotated 270-degrees. In other embodiments, differentsuitable rotations are utilized. The different phases of the 20 MHzsub-band signals result in reduced PAPR of OFDM symbols in the data unit300, in at least some embodiments and/or scenarios. In an embodiment, ifthe data unit that conforms to the first communication protocol is anOFDM data unit that occupies a cumulative bandwidth such as 20 MHz, 40MHz, 80 MHz, 160 MHz, 320 MHz, 640 MHz, etc., the HE-STF, the HE-LTFs,and the HE data portion occupy the corresponding whole bandwidth of thedata unit.

With continued reference to FIG. 12, each of the HE-SIG-A 1220 and theHE-SIG-B 1222 generally carries information about the format of the dataunit 1200, such as information needed to properly decode at least aportion of the data unit 1200, in an embodiment. In some embodiments,HE-SIG-A 1220 additionally includes information for client stations 25that are not intended receivers of the data unit 1200, such asinformation needed for medium protection from the client stations 25that are not intended receivers of the data unit 1200. On the otherhand, HE-SIG-B 1222 carries user-specific information individuallyneeded by each client station 25 that is an intended recipient of thedata unit 1200, in an embodiment. In an embodiment, HE-SIG-A 1220includes information needed to properly decode HE-SIG-B 1222, andHE-SIG-B 1222 includes information needed to properly decode datastreams in the data portion 1240 of the data unit 1200, in anembodiment. In some embodiments and/or scenarios, however, HE-SIG-Afield 1220 includes at least some of the information needed to decodethe data portion 1240.

In some embodiments, HE-SIG-B 1222 includes DL resource allocationinformation 1250 and UL ACK information 1260. In some embodiments, theUL ACK information 1260 is included in a single field or is spreadamongst several fields within the HE-SIG-B 1222. In some embodimentsand/or scenarios, the UL ACK information 1260 includes an indication ofa duration (in time) of an OFDMA/MU-MIMO transmission in the UL that isto be used by client devices to acknowledge the MU DL PPDU 1200. In someembodiments and/or scenarios, the UL ACK information 1260 also includesindication(s) of subchannels to be used by multiple client devices togenerate the OFDMA/MU-MIMO transmission in the UL that is to be used byclient devices to acknowledge the MU DL PPDU 1200. In some embodimentsand/or scenarios, the UL ACK information 1260 also includesindication(s) of MCSs to be used by multiple client devices to generatethe OFDMA/MU-MIMO transmission in the UL that is to be used by clientdevices to acknowledge the MU DL PPDU 1200.

As discussed above, in some embodiments, the AP may include, in acontrol frame included in or associated with a MU DL PPDU, informationthat provides information to client devices to indicate to the clientdevices how to generate an OFDMA/MU-MIMO acknowledgment for the MU DLPPDU. FIG. 13 is a diagram of an example MU DL PPDU 1300 and anassociated sync frame 1304 that may be utilized by the AP, according tosome embodiments. In an embodiment, the AP 14 is configured to generateand transmit to multiple client stations using OFDMA and/or MU-MIMO,according to an embodiment. The data unit 1300 conforms to the HEcommunication protocol and occupies a suitable bandwidth such as 20 MHz,40 MHz, 80 MHz, 160 MHz, 320 MHz, 640 MHz, for example, or othersuitable bandwidths, in other embodiments.

The MU DL PPDU 1300 includes a PHY preamble 1308 and a PHY data portion1312. The SYNC frame 1304 includes an MPDU 1320. The MPDU 1320 includesa MAC header 1324 and UL ACK information 1328.

In some embodiments, the UL ACK information 1328 is included in a singlefield or is spread amongst several fields within the MPDU 1320. In someembodiments and/or scenarios, the UL ACK information 1328 includes anindication of a duration (in time) of an OFDMA/MU-MIMO transmission inthe UL that is to be used by client devices to acknowledge the MU DLPPDU 1300. In some embodiments and/or scenarios, the UL ACK information1328 also includes indication(s) of subchannels to be used by multipleclient devices to generate the OFDMA/MU-MIMO transmission in the UL thatis to be used by client devices to acknowledge the MU DL PPDU 1300. Insome embodiments and/or scenarios, the UL ACK information 1328 alsoincludes indication(s) of MCSs to be used by multiple client devices togenerate the OFDMA/MU-MIMO transmission in the UL that is to be used byclient devices to acknowledge the MU DL PPDU 1300.

In an embodiment, the UL ACK information 1328 is included in a MAC dataportion of the MPDU 1320. In another embodiment, the UL ACK information1328 is included in the MAC header 1324.

In an embodiment, the SYNC frame 1304 is included in a PPDU separatefrom the MU DL PPDU 1300. In another embodiment, the SYNC frame 1304 isincluded in the MU DL PPDU 1300. For example, in an embodiment, the SYNCframe 1304 is included in an A-MPDU within the PHY data 1312. In variousembodiments, the A-MPDU has a format such as discussed above withrespect to FIGS. 7, 8A, and 8B.

In some embodiments, the MAC header 1324 includes a frame control field1350, a duration/ID field 1354, a receiver address field 1358, and atransmitter address field. In various embodiments, any one of, or anycombination of two or more of, the following fields are omitted from theMAC header 1324: the duration/ID field, the receiver address field 1358,and/or the transmitter address field 1362.

The MPDU 1320 also includes a frame body 1366 that includes the UL ACKinformation field 1328, in an embodiment. The MPDU 1320 also includes aframe check sequence field 1320, in an embodiment.

In FIG. 13, example lengths of the fields of the MPDU 1320 areillustrated. In other embodiments, other suitable lengths are utilized.

FIG. 14 is a diagram of an example transmission sequence 1400 in a WLAN,such as the WLAN 10 of FIG. 1, according to an embodiment, in which anAP, such as the AP 14, transmits a DL OFDMA communication frame tomultiple client stations, such as multiple ones of the client stations25, during a TXOP 1402.

The AP 14 generates and transmits a DL OFDMA/MU-MIMO communication frame1404, in an embodiment. In an embodiment, the communication frame 1404comprises respective data 1406 for multiple client devices. In anillustrative embodiment, the data 1106 comprise respective A-MPDUs 1406.In an embodiment, the communication frame 1404 spans a bandwidth of aprimary channel (e.g., a primary 20 MHz channel) of the WLAN 10 andmultiple other secondary channels (e.g., 20 MHz channels) of the WLAN10, i.e., the communication frame 1404 spans a bandwidth of a compositechannel comprising the primary channel and one or more secondarychannels.

In an embodiment, some of the client devices to which data transmissions1406 correspond generates and transmit respective ACK or BA portion aspart of an UL OFDMA transmission 1408 responsive to the communicationframe 1404. For example, in an embodiment, some client devices to whichdata transmissions 1406 corresponds generate and transmit respective ACKor BA portions 1412 a defined time period (e.g., a SIFS or anothersuitable time period) after the end of the communication frame 1404. Inan embodiment, some client devices generate and transmit respective ACKor BA portions 1412 in respective frequency blocks within acommunication channel spanned by the MU DL transmission.

On the other hand, the transmission corresponding to A-MPDU 1406-4 toSTA3 experiences and therefore STA3 does not receive the A-MPDU 1406-4correctly. In some scenarios, STA3 may receive the PHY headercorresponding to the MU DL PPDU 1404 correctly, but does not a dataportion of the MU DL PPDU 1404 correctly due to a collision that occursafter receive of the PHY header, for example. In an embodiment, when aSTA3 receives at least the HE-SIGB of the MU DL PPDU 1404 correctly, theSTA3 transmits an indication 1416 during the OFDMA ACK transmission1408, where the indication 1416 indicates to the AP that the STA3received at least the HE-SIGB of the MU DL PPDU 1404 correctly. This mayindicate to the AP, for example, that the MCS utilized by the AP totransmit to the STA3 is appropriate, in some embodiments.

The indication 1416 may comprise one of or any suitable combination oftwo or more of padding, padding with an A-MPDU delimiter, a QoS Nullframe, etc. In an embodiment, a suitable indicator 1416 is generated ina 20 MHz channel and then duplicated to one or more other 20 MHzchannels, if needed.

In the example of FIG. 14, STA0-STA2, STA4, and STA5 participate in theOFDMA transmission 1408, while STA3 transmits a suitable indication1416.

After receiving the UL transmission 1416, the AP determines that STA3received at least the HE-SIGB of the MU DL 1404 correctly, but did notreceive the A-MPDU 1406-4 correctly.

In some embodiments, each client device determines which OFDMsubchannels on which to transmit as part of the OFDMA acknowledgmentbased on the subchannels corresponding to the client used in the MU DLtransmission.

In an embodiment, if the number of client devices in the MU DLtransmission (Num_STA) is less than or equal to the number of 20 MHzchannels used in the MU DL transmission (Num_20 MHz), the followingprocedure is utilized by each client device to determine on which 20 MHzchannel to transmit as part of the OFDMA acknowledgment. An integer part(n) of dividing Num_20 MHz by Num_STA is determined. A remainder (r) ofdividing Num_20 MHz by Num_STA is determined. For client devices forwhich a position within the MU DL transmission (x) is smaller than r,the client device utilizes, in the OFDMA acknowledgment, 20 MHz channelsat positions x*(n+1) to (x+1)*(n+1)−1. For client devices for which aposition within the MU DL transmission (x) is greater than or equal tor, the client device utilizes, in the OFDMA acknowledgment, 20 MHzchannels at positions r*(n+1)+(x−r)*n to r*(n+1)+(x+1−r)*n−1.

In another embodiment, if the Num_STA is less than or equal to Num_20MHz, each client device utilizes the same bandwidth as used fortransmitting to the client in the MU DL transmission.

In an embodiment, if Num_20 MHz=1 and Num_STA>1, then the 20 MHz channelis allocated into nine groups of 26 OFDM subchannels, and the ninegroups of subchannels are assigned to the client devices utilizing asuitable technique. For example, in an embodiment, the nine groups ofsubchannels are assigned to the client devices in a manner similar tothe technique for allocating 20 MHz channels when Num_STA is less thanor equal to Num_20 MHz as discussed above.

In an embodiment, if Num_STA is greater than Num_20 MHz, the followingprocedure is utilized by each client device to determine on which OFDMchannels to transmit as part of the OFDMA acknowledgment. An integerpart (n) of dividing Num_STA by Num_20 MHz is determined. A remainder(r) of dividing Num_STA by Num_20 MHz is determined.

Client devices are assigned to 20 MHz channels. For example, for a 20MHz channel at position x, if x<r, a client device is assigned to thechannel at position x if the position of the client device within the MUDL transmission (p) satisfies: p>=x*(n+1) and p<(x+1)*(n+1)−1. If x>=r,a client device is assigned to the channel at position x if the positionof the client device within the MU DL transmission (p) satisfies:p>=r*(n+1)+(x−r)*n and p<r*(n+1)+(x+1−r)*n−1.

In an embodiment, after client devices are assigned to 20 MHz channels,the client devices assigned to each 20 MHz channel are assigned togroups of 26 OFDM subchannels within the 20 MHz channel using atechnique such as discussed above when Num_20 MHz=1 and Num_STA>1.

As discussed above, in some embodiments, the AP may include, in acontrol frame included in or associated with a MU DL PPDU, informationthat indicates to the client devices how to generate an OFDMA/MU-MIMOacknowledgment for the MU DL PPDU. For example, as discussed withreference to FIG. 12, such information may be included in a PHY header(e.g., in the HE-SIGB field or another suitable field) of a downlinkdata unit, according to some embodiments. As another example, asdiscussed with reference to FIG. 13, such information may be included ina SYNC frame, according to some embodiments. In some embodiments, theSYNC frame may be included in an A-MPDU along with data and/or othercontrol frames. In some embodiments, the SYNC frame may be in a separatebroadcast SYNC, or trigger frame.

FIG. 15 is a diagram of an example information element 1500 that may beincluded in a downlink transmission, where the information element 1500includes information that indicates to the client devices how togenerate an OFDMA/MU-MIMO acknowledgment for the MU DL PPDU, accordingto an embodiment. In some embodiments, the information element 1500 isincluded in a PHY header (e.g., in the HE-SIGB field or another suitablefield) of a downlink data unit. In some embodiments, the informationelement 1500 is included in a SYNC frame, which in turn is included inan A-MPDU along with data and/or other control frames. In someembodiments, the information element 1500 is included in a separatebroadcast SYNC or trigger frame.

The information element 1500 includes a field 1504 that indicates alength of the UL PPDU acknowledgment data unit. In an embodiment, thefield 1504 indicates a number of OFDM symbols. The information element1500 also includes a field 1508 that indicates whether client devicesshould use the same resource allocation (e.g., OFDM subcarriers,subchannels, etc.) for the acknowledgment as was assigned for the DLtransmission that is to be acknowledged, in an embodiment. Theinformation element 1500 also includes a field 1512 that indicates theresource allocation (e.g., OFDM subcarriers, subchannels, etc.) for aclient device to use for the acknowledgment, in an embodiment. In anembodiment, the resource allocation field 1512 indicates i) a startlocation of a resource unit (RU) (e.g., a starting OFDM subcarrierindex, an edge of a subchannel, etc.) and ii) a width of the RU (e.g., anumber of OFDM subcarriers, a bandwidth, etc.).

In an embodiment, the field 1504 is five bits in length. In otherembodiments, the field 1504 is a different suitable number of bits(e.g., 2, 3, 4, 6, 7, 8, 9, 10, 11, 12. etc.). In an embodiment, thefield 1508 is one bit. In other embodiments, the field 1508 is adifferent suitable number of bits (e.g., 2, 3, 4, 5, 6, etc.). In anembodiment, the field 1512 is ten bits in length. In other embodiments,the field 1504 is a different suitable number of bits (e.g., 11, 12, 13,14, 15, 16, 17, 18, 19, 20, etc.).

In some embodiments, the fields illustrated in FIG. 15 are included inan information element having additional information. For example, FIG.16 is a diagram of an example resource allocation information element1600, according to an embodiment. The information element 1600 includesa transmit power field 1604 that includes an indication of a transmitpower to be used by a client device during an UL OFDMA transmission. Theinformation element 1600 also includes the fields 1504, 1508, and 1512discussed above with reference to FIG. 15. The information element 1600further includes: a SU/MU-MIMO field 1616 that indicates whether thetransmission is utilize MU MIMO; a guard interval (GI) mode field 1620that indicates a GI mode to be utilized; an LTF type field 1624 thatindicates a type of LTF to be used; an LTF number field 1628 thatindicates a number of LTFs to be included; a number of spatial streams(Nsts) field 1632 that indicates a number of spatial streams to be used;an MCS field 1636 specifying an MCS to be used; a transmit beamforming(TxBF) field 1640 that indicates whether TxBF is to be used; aspace-time stream block coding (STBC) field 1644 that indicates whetherSTBC is to be utilized; a low density parity check (LDPC) field 1648that indicates whether LDPC is to be utilized; and a traffic class (TC)field 1652 that indicates a TC to be included in the transmission.

In some embodiments, some of the parameters indicated in the informationelement 1600 can be implicitly determined by a client device based onthe downlink transmission that is to be acknowledged. For example, in anembodiment, each client device receiving a MU DL transmission are awareof the RUs allocated to all of the client devices of the MU DLtransmission and the MCSs used for all of the client devices in the MUDL transmission. In such an embodiment, each client device can determinethe longest acknowledgment transmission amongst all of the clientdevices that are to acknowledge the MU DL transmission because theMCS(s) for the UL acknowledgements are restricted by the MCS(s) used inthe MU DL transmission.

In an embodiment, a subset 1660 of fields is omitted from theinformation element when the field 1508 is set to indicate that, foreach client device, the same RU used in the MU DL is to be used whenacknowledging the MU DL. In an embodiment, the field 1508 also indicatesthat, for each client device, other parameters used in the MU DL are tobe the same when acknowledging the MU DL (e.g., MCS, number of spatialstreams, GI mode, other parameters specified in the subset 1660, etc.).

Although FIG. 16 illustrates example numbers of bits for each field inthe information element 1600, other suitable numbers of bits may beutilized. For example, in an embodiment, the TX power field 1604 is asuitable number of bits other than ten. As another example, in anembodiment, the field 1624 is a suitable number of bits other than two.As another example, in an embodiment, the field 1632 is a suitablenumber of bits other than three.

In an embodiment, the MCS field 1636 is omitted. For example, in someembodiments, a client device determines an MCS to use based on the ULPPDU length (field 1504) and the bandwidth.

FIG. 17A is a diagram of an example field 1700 that is used to indicatea sub-band within an OFDMA transmission, where the sub-band correspondsto a transmission to/from a client device, according to an embodiment.In some embodiments, UL acknowledgment information discussed aboveincludes the field 1700. For instance, in some embodiments, the field1512 discussed above includes the field 1700. In some embodiments, thefield 1250 and/or the field 1260 (FIG. 12) includes the field 1700. Insome embodiments, the field 1328 (FIG. 13) includes the field 1700.

The field 1700 includes a field 1704 to indicate whether the sub-band isless (sometimes referred to as an RU) than 20 MHz. In an embodiment, thefield 1704 is one bit. In other embodiments, the field is a suitablesize larger than 1 bit (e.g., 2, 3, 4, 5, etc., bits).

The field 1700 includes a field 1708 to indicate a start location of anRU, and a field 1712 to indicate a width of the RU. In an embodiment,fields 1708 and 1712 are interpreted differently depending on whetherfield 1704 indicates that the RU is less than 20 MHz or greater than 20MHz. In one embodiment, the field 1708 is seven bits and the field 1712is two bits. In other embodiments, the field 1708 is another suitablesize (e.g., 5, 6, 8, 9, 10, etc., bits) and/or the field 1712 is anothersuitable size (e.g., 3, 4, 5, etc., bits). Table 1 is an example ofencodings of the fields 1708 and 1712 according to an illustrativeembodiment. In other embodiments, other suitable encodings are utilized.

TABLE 1 Field 1704 0 1 (RU is greater than or (RU is less than 20 MHz)equal to 20 MHz) Start of RU 3 most significant bits 3 most significantbits field 1708 indicate 20 MHz channel indicate 20 MHz channel in whichRU starts. in which RU is included. 4 least significant bits 4 leastsignificant bits are set to zero. indicate group of 26-tones in which RUstarts. Width of RU 00 = 20 MHz 00 = 26 OFDM tones field 1712 01 = 40MHz 01 = 52 OFDM tones 10 = 60 MHz 10 = 78 OFDM tones 11 = 80 MHz 11 =104 OFDM tones

FIG. 17B is a diagram of an example field 1750 that is used to indicatea sub-band within an OFDMA transmission and also one or more spatialstreams, according to an embodiment. The field 1750 is similar to thefield 1700 of FIG. 17A, and like-numbered elements are not discussed forpurposes of brevity.

In some embodiments, UL acknowledgment information discussed aboveincludes the field 1750. For instance, in some embodiments, the field1512 discussed above includes the field 1750. In some embodiments, thefield 1250 and/or the field 1260 (FIG. 12) includes the field 1750. Insome embodiments, the field 1328 (FIG. 13) includes the field 1750.

The field 1750 includes a spatial stream indication field 1754. Forexample, in some embodiments in which a DL OFDMA frame includes aMU-MIMO transmission, recipients of the MU-MIMO transmission acknowledgethe MU-MIMO transmission with an UL MU-MIMO transmission in whichdifferent client devices transmit via different spatial streams. In someembodiments, the AP may assign different client devices to differentspatial streams and inform the client devices of the assignments usingthe field 1754.

FIG. 18A is a diagram of another example field 1800 that is used toindicate a sub-band within an OFDMA transmission, where the sub-bandcorresponds to a transmission to/from a client device, according to anembodiment. In some embodiments, UL acknowledgment information discussedabove includes the field 1800. For instance, in some embodiments, thefield 1512 discussed above includes the field 1800. In some embodiments,the field 1250 and/or the field 1260 (FIG. 12) includes the field 1800.In some embodiments, the field 1328 (FIG. 13) includes the field 1800.

The field 1800 includes a field 1804 to indicate a 20 MHz channel inwhich an RU is located (if the RU is less than 20 MHz) or a 20 MHzchannel that is the start of the RU (if the RU is greater than or equalto 20 MHz). The field 1800 also includes a field 1808 to indicate awidth of the RU and/or a starting group of 26 OFDM tones within a 20 MHzchannel. In one embodiment, the field 1808 is set to an index value thatindicates an RU from a set of allowable RUs for a given starting 20 MHzchannel. For example, FIG. 19 is a diagram of an example set ofallowable RUs for a given starting 20 MHz channel, according to anembodiment. Thus, in an embodiment, the field 1808 is an index valueindicating one of a plurality RUs, including RUs of different bandwidthsand RUs having different positions within a 20 MHz communication channel(e.g., the allowable RUs illustrated in FIG. 19 or another suitable setof allowable RUs), given the 20 MHz channel indicated by the field 1804.Although FIGS. 18 and 19 were discussed in the context of a 20 MHzcommunication channel being indicated by the field 1804 and groups of 26OFDM tones, communication channels of a suitable bandwidth other than 20MHz and/or suitable groups of OFDM tones other than 26 are used in otherembodiments.

In one embodiment, the field 1804 is three bits and the field 1808 isfive bits. In other embodiments, the field 1804 is another suitable size(e.g., 2, 4, 5, 6, 8, 9, 10, etc., bits) and/or the field 1808 isanother suitable size (e.g., 3, 4, 6, 7, 8, 9, 10, etc., bits). Table 2is an example of encodings of the fields 1804 and 1808 according to anillustrative embodiment. In other embodiments, other suitable encodingsare utilized.

TABLE 2 Channel Index field 1804 Indicates 20 MHz channel in which an RUis located (if the RU is less than 20 MHz) or a 20 MHz channel that isthe start of the RU (if the RU is greater than or equal to 20 MHz) Starttone and width of RU Index indicating RU from field 1808 set ofallowable RUs

FIG. 18B is a diagram of an example field 1850 that is used to indicatea sub-band within an OFDMA transmission and also one or more spatialstreams, according to an embodiment. The field 1850 is similar to thefield 1800 of FIG. 18A, and like-numbered elements are not discussed forpurposes of brevity.

In some embodiments, UL acknowledgment information discussed aboveincludes the field 1850. For instance, in some embodiments, the field1512 discussed above includes the field 1850. In some embodiments, thefield 1250 and/or the field 1260 (FIG. 12) includes the field 1850. Insome embodiments, the field 1328 (FIG. 13) includes the field 1850.

The field 1850 includes a spatial stream indication field 1854. Forexample, in some embodiments in which a DL OFDMA frame includes aMU-MIMO transmission, recipients of the MU-MIMO transmission acknowledgethe MU-MIMO transmission with an UL MU-MIMO transmission in whichdifferent client devices transmit via different spatial streams. In someembodiments, the AP may assign different client devices to differentspatial streams and inform the client devices of the assignments usingthe field 1854.

In some embodiments, A-MPDUs are used in OFDMA transmissions, andA-MPDUs include only one control frame or may aggregate one or morecontrol frames. For instance, FIG. 20A illustrates an example A-MPDU2000 that includes an ACK frame 2004, according to an embodiment. FIG.20B illustrates an example A-MPDU 2020 that includes an ACK frame 2024and a resource request frame 2028, according to an embodiment. FIG. 20Cillustrates an example A-MPDU 2040 that includes an ACK frame 2044 and async or trigger frame 2048, according to an embodiment.

In some embodiments, ACKs and/or BAs of OFDMA/MU-MIMO transmissions maybe shortened to reduce channel overhead. For example, in someembodiments, the receiver of an ACK/BA may already know a length of theACK/BA. For example, in some embodiments, an A-MPDU delimiter can beomitted with an ACK/BA. As another example, a duration field is omittedwhen a duration field is includes in a PHY preamble (e.g., in an HE-SIGfield), in some embodiments. In some embodiments, one or more addressesare omitted and/or shortened. For example, in some embodiments, areceiver address (RA) is omitted. In some embodiments, a transmitteraddress is shortened, such as by replacing an MAC address with an AID.In some embodiments, an identifier of the frame or frames beingacknowledged (e.g., a sequence number, a scramble seed-FCS combination,etc.) may replace an address field.

FIG. 21A is a diagram of an example ACK frame 2100 that is utilized insome embodiments. The ACK frame 2100 includes a frame control field2104, a transmitter address field 2108, and an FCS field 2112. Thus, inan embodiment, the ACK frame 2100 omits an A-MPDU delimiter, aduration/ID field, and a receiver address field. In an embodiment, thetransmitter address field 2108 includes a MAC address of thetransmitter. In another embodiment, the transmitter address field 2108includes an AID of the transmitter. Although FIG. 21A illustratesexample field sizes, in other embodiments, other suitable field sizesare utilized.

FIG. 21B is a diagram of an example BA frame 2150 that is utilized insome embodiments. The BA frame 2150 includes a frame control field 2154,a transmitter address field 2158, a BA control field 2162, a BA SSCfield 2164, a BA bitmap field 2166, and an FCS field 2170. Thus, in anembodiment, the ACK frame 2150 omits an A-MPDU delimiter, a duration/IDfield, and a receiver address field. In an embodiment, the transmitteraddress field 2158 includes a MAC address of the transmitter. In anotherembodiment, the transmitter address field 2158 includes an AID of thetransmitter. Although FIG. 21B illustrates example field sizes, in otherembodiments, other suitable field sizes are utilized.

FIG. 22 is a flow diagram of an example method 2200 for transmitting aMU DL transmission, according to an embodiment. In some embodiments, themethod 2200 is implemented by the AP 14 (FIG. 1). For example, in someembodiments, the network interface device 16 is configured to implementthe method 2200. In other embodiments, another suitable networkinterface device is configured to implement the method 2200.

At block 2204, an MU-MIMO signal is generated, where MU-MIMO includesindependent data for multiple second communication devices modulated ondifferent spatial streams. In an embodiment, the MU-MIMO is signal is aMU DL signal.

At block 2208, the MU-MIMO signal is included in a MU PHY data unit andthe MU PHY data unit is transmitted to multiple communication devices.For example, in an embodiment, the MU-MIMO signal is included in a DLMU-MIMO PHY data unit. As another example, in an embodiment, the MU-MIMOsignal is included in a DL OFDMA PHY data unit.

At block 2212, OFDMA PHY data unit is received from the multiplecommunication devices, the OFDMA PHY data unit corresponding to anacknowledgment of the MU PHY data unit by the multiple communicationdevices.

At block 2216, the OFDMA PHY data unit is processed to determine whetherthe multiple communication devices received the multi-user PHY dataunit.

In some embodiments, different frequency portions of the OFDMA PHY dataunit correspond to different second communication devices, and themethod 2200 further comprises determining which frequency portionscorrespond to which communication devices, and including in the MU PHYdata unit information that indicates which frequency portions correspondto which communication devices so that each communication device candetermine in which frequency portion the communication device is totransmit as part of the OFDMA.

In some embodiments, the method 2200 further comprises determining,prior to receiving the OFDMA PHY data unit, a duration of the OFDMA PHYdata unit, and including in the MU PHY data unit information thatindicates the duration of the OFDMA PHY data unit so that eachcommunication device can generate a respective portion of the OFDMA PHYdata unit so that the respective portion has a respective durationsubstantially equal to the indicated duration.

FIG. 23 is a flow diagram of an example method 2300 for receiving a MUDL transmission, according to an embodiment. In some embodiments, themethod 2300 is implemented by a client device 25 (FIG. 1). For example,in some embodiments, the network interface device 27 is configured toimplement the method 2300. In other embodiments, another suitablenetwork interface device is configured to implement the method 2300.

At block 2304, an MU PHY data unit is received, the MU PHY data unitincluding an MU-MIMO signal with independent data for multiplecommunication devices. In an embodiment, the MU PHY data unit is a MU DLsignal. In an embodiment, the MU PHY data unit is a DL MU-MIMO PHY dataunit. As another example, in an embodiment, the MU PHY data unit is a DLOFDMA PHY data unit.

At block 2308, the MU PHY data unit received at block 2304 is processedto determine first information, in the MU PHY data unit, that indicatesin which frequency portion to transmit, as part of an OFDMA PHY dataunit, that the multiple communication devices are to transmit in orderto acknowledge the MU PHY data unit received at block 2304.

At block 2312, a portion of the OFDMA PHY data unit is generated so thatthe portion of the OFDMA PHY data unit corresponds to the frequencyportion indicated by the first information in the MU PHY data unit.

At block 2316, the portion of the OFDMA PHY data unit is transmittedwhile the other communication devices transmit one or more otherportions of the OFDMA PHY data unit to acknowledge the MU PHY data unit.

In some embodiments, the method further comprises processing the MU PHYdata unit to determine second information, in the MU PHY data unit, thatindicates a duration of the OFDMA PHY data unit that the multiplecommunication devices are to transmit to acknowledge the MU PHY dataunit. In such embodiments, the portion of the OFDMA PHY data unit isgenerated at block 2312 so that the duration is substantially equal tothe duration indicated by the second information in the MU PHY dataunit.

FIG. 24 is a flow diagram of an example method 2400 for transmitting aMU DL transmission, according to an embodiment. In some embodiments, themethod 2400 is implemented by the AP 14 (FIG. 1). For example, in someembodiments, the network interface device 16 is configured to implementthe method 2400. In other embodiments, another suitable networkinterface device is configured to implement the method 2400.

At block 2404, an MU PHY data unit is generated, where MU PHY data unitincludes independent data for multiple communication devices. In anembodiment, the MU PHY data unit is signal is a DL OFDMA PHY data unit.In an embodiment, the DL OFDMA PHY data unit includes an MU-MIMOtransmission. In an embodiment, the MU PHY data unit is signal is a DLMU-MIMO PHY data unit.

At block 2208, respective control frames corresponding to at least someof the communication devices are generated, wherein the respectivecontrol frames are configured to prompt the at least some of thecommunication devices to transmit an OFDMA PHY data unit to acknowledgethat the at least some of the communication devices received the MU PHYdata unit.

At block 2412, the MU PHY data unit is transmitted to the multiplecommunication devices.

At block 2416, the respective control frames are transmitted to themultiple communication devices. In an embodiment, the respective controlframes are included in the MU PHY data unit, and block 2412 includesblock 2416. In an embodiment, the respective control frames are includedin a PHY data unit separate from the MU PHY data unit.

At block 2420, OFDMA PHY data unit is received from the multiplecommunication devices, the OFDMA PHY data unit corresponding to anacknowledgment of the MU PHY data unit by the multiple communicationdevices.

At block 2424, the OFDMA PHY data unit is processed to determine whetherthe multiple communication devices received the multi-user PHY dataunit.

In some embodiments, different frequency portions of the OFDMA PHY dataunit correspond to different second communication devices, and themethod 2400 further comprises determining which frequency portionscorrespond to which communication devices, and including in therespective control frames information that indicates which frequencyportions correspond to which communication devices so that eachcommunication device can determine in which frequency portion thecommunication device is to transmit as part of the OFDMA.

In some embodiments, the method 2400 further comprises determining,prior to receiving the OFDMA PHY data unit, a duration of the OFDMA PHYdata unit, and including in the respective control frames informationthat indicates the duration of the OFDMA PHY data unit so that eachcommunication device can generate a respective portion of the OFDMA PHYdata unit so that the respective portion has a respective durationsubstantially equal to the indicated duration.

FIG. 25 is a flow diagram of an example method 2500 for receiving a MUDL transmission, according to an embodiment. In some embodiments, themethod 2500 is implemented by a client device 25 (FIG. 1). For example,in some embodiments, the network interface device 27 is configured toimplement the method 2500. In other embodiments, another suitablenetwork interface device is configured to implement the method 2500.

At block 2504, an MU PHY data unit is received, the MU PHY data unitincluding independent data for multiple communication devices. In anembodiment, the MU PHY data unit is a MU DL signal. In an embodiment,the MU PHY data unit is a DL MU-MIMO PHY data unit. As another example,in an embodiment, the MU PHY data unit is a DL OFDMA PHY data unit. Inan embodiment, the DL OFDMA PHY data unit includes an MU-MIMOtransmission.

At block 2508, a control frame is received, the control frame forprompting transmission of an OFDMA PHY Data Unit to acknowledge the MUPHY data unit received at block 2504. In an embodiment, the controlframe is included in the MU PHY data unit received at block 2504, andthus block 2504 includes block 2508. In other embodiments, the controlframe is received in a PHY data unit separate from the MU PHY data unitreceived at block 2504.

At block 2512, the control frame received at block 2508 is processed todetermine first information that indicates in which frequency portion totransmit, as part of an OFDMA PHY data unit, that the multiplecommunication devices are to transmit in order to acknowledge the MU PHYdata unit received at block 2504.

At block 2516, a portion of the OFDMA PHY data unit is generated so thatthe portion of the OFDMA PHY data unit corresponds to the frequencyportion indicated by the first information in the control frame.

At block 2520, the portion of the OFDMA PHY data unit is transmittedwhile the other communication devices transmit one or more otherportions of the OFDMA PHY data unit to acknowledge the MU PHY data unit.

In some embodiments, the method further comprises processing the controlframe to determine second information that indicates a duration of theOFDMA PHY data unit that the multiple communication devices are totransmit to acknowledge the MU PHY data unit. In such embodiments, theportion of the OFDMA PHY data unit is generated at block 2516 so thatthe duration is substantially equal to the duration indicated by thesecond information in the MU PHY data unit.

FIG. 26 is a flow diagram of an example method 2600 for receiving a MUDL transmission, according to an embodiment. In some embodiments, themethod 2600 is implemented by a client device 25 (FIG. 1). For example,in some embodiments, the network interface device 27 is configured toimplement the method 2600. In other embodiments, another suitablenetwork interface device is configured to implement the method 2600.

At block 2604, a first OFDMA PHY data unit is received, the first OFDMAPHY data unit including independent data for multiple communicationdevices, including a first communication device. In an embodiment, datacorresponding to the first communication device is in included in thefirst OFDMA PHY data unit in a first frequency subband within acommunication channel spanned by the first OFDMA PHY data unit. In anembodiment, the OFDMA PHY data unit is a MU DL signal. In an embodiment,the DL OFDMA PHY data unit includes an MU-MIMO transmission.

At block 2608, a second frequency subband in which the firstcommunication device is to transmit as part of a second OFDMA PHY dataunit is determined, the second OFDMA PHY data unit for acknowledging, bythe first communication device and one or more second communicationdevices, the first OFDMA PHY data unit, wherein the second frequencysubband is determined based on i) a number of the first communicationdevice and the one or more second communication devices, and ii) anumber of component communication channels spanned by the first OFDMAPHY data unit.

In some embodiments, the second frequency subband is determined furtherbased on a position of the first frequency subband within thecommunication channel spanned by the first OFDMA PHY data unit. In someembodiments, the integer part and the remainder of the division of i)the number of component communication channels spanned by the firstOFDMA PHY data unit by ii) the number of the first communication deviceand the one or more second communication devices is determined when thenumber of component communication channels spanned by the first OFDMAPHY data unit is greater than or equal to the number of the firstcommunication device and the one or more second communication devices.

In some embodiments, determining the second frequency subband includes:determining an integer part of a division of i) the number of componentcommunication channels spanned by the first OFDMA PHY data unit by ii)the number of the first communication device and the one or more secondcommunication devices; and determining a remainder of the division;wherein the second frequency subband is determined using the integerpart of the division and the remainder.

In some embodiments, determining the second frequency subband includes:determining an integer part of a division of i) the number of the firstcommunication device and the one or more second communication devices byii) the number of component communication channels spanned by the firstOFDMA PHY data unit; and determining a remainder of the division;wherein the second frequency subband is determined using the integerpart of the division and the remainder. In some embodiments, the integerpart and the remainder of the division of i) the number of the firstcommunication device and the one or more second communication devices byii) the number of component communication channels spanned by the firstOFDMA PHY data unit is determined when the number of componentcommunication channels spanned by the first OFDMA PHY data unit is lessthan the number of the first communication device and the one or moresecond communication devices.

At block 2612, a portion of the second OFDMA PHY data unit is generatedso that the portion of the second OFDMA PHY data unit corresponds to thesecond frequency subband.

At block 2616, the portion of the second OFDMA PHY data unit istransmitted while the other communication devices transmit one or moreother portions of the OFDMA PHY data unit to acknowledge the first OFDMAPHY data unit.

In some embodiments, the method further comprises processing the controlframe to determine second information that indicates a duration of theOFDMA PHY data unit that the multiple communication devices are totransmit to acknowledge the MU PHY data unit. In such embodiments, theportion of the OFDMA PHY data unit is generated at block 2516 so thatthe duration is substantially equal to the duration indicated by thesecond information in the MU PHY data unit.

In various embodiments, techniques, PHY data unit formats, fields, etc.,described above are utilized with one or more of the methods describedwith reference to FIGS. 22-26.

In an embodiment, a method for communicating in a wireless communicationnetwork includes: generating, at a first communication device, amulti-user multiple input-multiple output (MU-MIMO) signal havingindependent data for multiple second communication devices;transmitting, with the first communication device, the MU-MIMO signal ina multi-user physical layer (PHY) data unit to the multiple secondcommunication devices; receiving, at the first communication device, anorthogonal frequency division multiple access (OFDMA) PHY data unit fromthe multiple second communication devices, the OFDMA PHY data unitcorresponding to an acknowledgment of the multi-user PHY data unit bythe multiple second communication devices; and processing, at the firstcommunication device, the OFDMA PHY data unit to determine that themultiple second communication devices received the multi-user PHY dataunit.

In other embodiments, the method includes any suitable combination ofone or more of the following features.

Respective frequency portions of the OFDMA PHY data unit correspond withrespective second communication devices; the method further comprisesdetermining, at the first communication device, which frequency portionscorrespond to which second communication devices; and generating the MUPHY data unit comprises including in the MU PHY data unit informationthat indicates which frequency portions correspond to which secondcommunication devices so that each second communication device candetermine in which frequency portion the second communication device isto transmit.

The method further comprises determining, at the first communicationdevice and prior to receiving the OFDMA PHY data unit, a duration of theOFDMA PHY data unit; and wherein generating the MU PHY data unitcomprises including in the MU PHY data unit information that indicatesduration of the OFDMA PHY data unit so that each second communicationdevice can generate a respective portion of the OFDMA PHY data unit sothat the respective portion has a respective duration substantiallyequal to the indicated duration.

The MU PHY data unit is a DL OFDMA data unit that includes the MU-MIMOsignal.

The MU PHY data unit is a MU-MIMO PHY data unit.

In another embodiment, an apparatus comprises a network interface devicehaving one or more integrated circuits configured to: generate amulti-user multiple input-multiple output (MU-MIMO) signal havingindependent data for multiple communication devices, transmit theMU-MIMO signal in a multi-user physical layer (PHY) data unit to themultiple communication devices, receive an orthogonal frequency divisionmultiple access (OFDMA) PHY data unit from the multiple communicationdevices, the OFDMA PHY data unit corresponding to an acknowledgment ofthe multi-user PHY data unit by the multiple communication devices, andprocess the OFDMA PHY data unit to determine that the multiplecommunication devices received the multi-user PHY data unit.

In other embodiments, the apparatus includes any suitable combination ofone or more of the following features.

Respective frequency portions of the OFDMA PHY data unit correspond withrespective second communication devices; and the one or more integratedcircuits configured to determine which frequency portions correspond towhich second communication devices, and include in the MU PHY data unitinformation that indicates which frequency portions correspond to whichsecond communication devices so that each second communication devicecan determine in which frequency portion the second communication deviceis to transmit.

The one or more integrated circuits configured to: determine, prior toreceiving the OFDMA PHY data unit, a duration of the OFDMA PHY dataunit; and include in the MU PHY data unit information that indicatesduration of the OFDMA PHY data unit so that each second communicationdevice can generate a respective portion of the OFDMA PHY data unit sothat the respective portion has a respective duration substantiallyequal to the indicated duration.

The MU PHY data unit is a DL OFDMA data unit that includes the MU-MIMOsignal.

The MU PHY data unit is a MU-MIMO PHY data unit.

In another embodiment, a method for acknowledging a multi-user multipleinput-multiple output (MU-MIMO) transmission includes: receiving, at afirst communication device, a MU physical layer (PHY) data unit, the MUPHY data unit including an MU-MIMO signal with independent data for thefirst communication device and one or more second communication devices,the MU PHY data unit having been transmitted by a third communicationdevice; processing, at the first communication device, the MU PHY dataunit to determine first information, in the MU PHY data unit, thatindicates in which frequency portion the first communication device isto transmit as part of an orthogonal frequency division multiple access(OFDMA) PHY data unit that the first communication device and the one ormore second communication devices are to transmit to the thirdcommunication device in order to acknowledge the MU PHY data unit;generating, at the first communication device, a portion of the OFDMAPHY data unit so that the portion of the OFDMA PHY data unit correspondsto the frequency portion indicated by the first information in the MUPHY data unit; and transmitting, at the first communication device, theportion of the OFDMA PHY data unit while the one or more secondcommunication devices transmit one or more other portions of the OFDMAPHY data unit to acknowledge the MU PHY data unit.

In other embodiments, the method includes any suitable combination ofone or more of the following features.

The method further comprises: processing, at the first communicationdevice, the MU PHY data unit to determine second information, in the MUPHY data unit, that indicates a duration of the OFDMA PHY data unit thatthe first communication device and the one or more second communicationdevices are to transmit to the third communication device to acknowledgethe MU PHY data unit; wherein the first communication device generatesthe portion of the OFDMA PHY data unit so that the portion of the OFDMAPHY data unit has a duration substantially equal to the durationindicated by the second information in the MU PHY data unit.

The MU PHY data unit includes an aggregated media access control (MAC)protocol data unit (A-MPDU); and the first information and the secondinformation are included in a control frame within the A-MPDU.

The MU PHY data unit is a DL OFDMA data unit that includes the MU-MIMOsignal.

The MU PHY data unit is a MU-MIMO PHY data unit.

In another embodiment, an apparatus comprises a network interface devicehaving one or more integrated circuit devices configured to receive amulti-user (MU) physical layer (PHY) data unit, the MU PHY data unitincluding an MU-MIMO signal with independent data for a firstcommunication device and one or more second communication devices, theMU PHY data unit having been transmitted by a third communicationdevice, process the MU PHY data unit to determine first information, inthe MU PHY data unit, that indicates in which frequency portion thefirst communication device is to transmit as part of an orthogonalfrequency division multiple access (OFDMA) PHY data unit that the firstcommunication device and the one or more second communication devicesare to transmit to the third communication device in order toacknowledge the MU PHY data unit, generate a portion of the OFDMA PHYdata unit so that the portion of the OFDMA PHY data unit corresponds tothe frequency portion indicated by the first information in the MU PHYdata unit, and transmit the portion of the OFDMA PHY data unit while theone or more second communication devices transmit one or more otherportions of the OFDMA PHY data unit to acknowledge the MU PHY data unit.

In other embodiments, the apparatus includes any suitable combination ofone or more of the following features.

The one or more integrated circuits are configured to: process the MUPHY data unit to determine second information, in the MU PHY data unit,that indicates a duration of the OFDMA PHY data unit that the firstcommunication device and the one or more second communication devicesare to transmit to the third communication device to acknowledge the MUPHY data unit; generate the portion of the OFDMA PHY data unit so thatthe portion of the OFDMA PHY data unit has a duration substantiallyequal to the duration indicated by the second information in the MU PHYdata unit.

The MU PHY data unit includes an aggregated media access control (MAC)protocol data unit (A-MPDU); and the first information and the secondinformation are included in a control frame within the A-MPDU.

The MU PHY data unit is a DL OFDMA data unit that includes the MU-MIMOsignal.

The MU PHY data unit is a MU-MIMO PHY data unit.

In another embodiment, a method for communicating in a wirelesscommunication network includes: generating, at a first communicationdevice, a multi-user (MU) physical layer (PHY) data unit havingindependent data for multiple second communication devices; generating,at the first communication device, respective control framescorresponding to at least some of the second communication devices,wherein the respective control frames are configured to prompt the atleast some of the second communication devices to transmit an orthogonalfrequency division multiple access (OFDMA) PHY data unit to acknowledgethat the at least some of the second communication devices received theMU PHY data unit; transmitting, with the first communication device, theMU PHY data unit to the multiple second communication devices;transmitting, with the first communication device, the respectivecontrol frames to the multiple second communication devices; receiving,at the first communication device, the OFDMA PHY data unit from the atleast some of the second communication devices, the OFDMA PHY data unitcorresponding to an acknowledgment of the single MU PHY data unit by theat least some of the second communication devices; and processing, atthe first communication device, the OFDMA PHY data unit to determinethat the at least some of the multiple second communication devicesreceived the single MU PHY data unit.

In other embodiments, the method includes any suitable combination ofone or more of the following features.

The single MU PHY data unit is an OFDMA PHY data unit.

The single MU PHY data unit is a multi-user multiple input, multipleoutput (MU-MIMO) data unit.

Generating the MU PHY data unit comprises including in the MU PHY dataunit the respective control frames; and transmitting the MU PHY dataunit includes transmitting the respective control frames within the MUPHY data unit.

Respective frequency portions of the OFDMA PHY data unit correspond withrespective second communication devices; the method further comprisesdetermining, at the first communication device, which frequency portionscorrespond to which second communication devices; and generating therespective control frames comprises including, in the respective controlframes, information that indicates which frequency portions correspondto which second communication devices so that each second communicationdevice among the at least some of the second communication devices candetermine in which frequency portion the second communication device isto transmit.

The method further comprises: determining, at the first communicationdevice and prior to receiving the OFDMA PHY data unit, a duration of theOFDMA PHY data unit; and wherein generating the respective controlframes comprises including in the respective control frames informationthat indicates a duration of the OFDMA PHY data unit so that each secondcommunication device among the at least some of the second communicationdevices can generate a respective portion of the OFDMA PHY data unit sothat the respective portion has a respective duration substantiallyequal to the indicated duration.

An apparatus comprising: a network interface device having one or moreintegrated circuit devices configured to: generate a multi-user (MU)physical layer (PHY) data unit having independent data for multiplecommunication devices, generate respective control frames correspondingto at least some of the second communication devices, wherein therespective control frames are configured to prompt the at least some ofthe second communication devices to transmit an orthogonal frequencydivision multiple access (OFDMA) PHY data unit to acknowledge that theat least some of the communication devices received the MU PHY dataunit, transmit the MU PHY data unit to the multiple communicationdevices, transmit the respective control frames to the multiplecommunication devices, receive the OFDMA PHY data unit from the at leastsome of the communication devices, the OFDMA PHY data unit correspondingto an acknowledgment of the single MU PHY data unit by the at least someof the communication devices, and process the OFDMA PHY data unit todetermine that the at least some of the multiple communication devicesreceived the single MU PHY data unit.

In other embodiments, the apparatus includes any suitable combination ofone or more of the following features.

The single MU PHY data unit is an OFDMA PHY data unit.

The single MU PHY data unit is a multi-user multiple input, multipleoutput (MU-MIMO) data unit.

The one or more integrated circuit devices are configured to: include inthe MU PHY data unit the respective control frames; and transmit therespective control frames within the MU PHY data unit.

Respective frequency portions of the OFDMA PHY data unit correspond withrespective second communication devices; the one or more integratedcircuit devices are configured to determine which frequency portionscorrespond to which second communication devices, and include, in therespective control frames, information that indicates which frequencyportions correspond to which second communication devices so that eachsecond communication device among the at least some of the communicationdevices can determine in which frequency portion the secondcommunication device is to transmit.

The one or more integrated circuit devices are configured to: determine,prior to receiving the OFDMA PHY data unit, a duration of the OFDMA PHYdata unit; and include in the respective control frames information thatindicates a duration of the OFDMA PHY data unit so that eachcommunication device among the at least some of the communicationdevices can generate a respective portion of the OFDMA PHY data unit sothat the respective portion has a respective duration substantiallyequal to the indicated duration.

In another embodiment, a method for acknowledging a first orthogonalfrequency division multiple access (OFDMA) physical layer (PHY) dataunit includes: receiving, at a first communication device, the firstOFDMA PHY data unit, the first OFDMA PHY data unit having independentdata for the first communication device and one or more secondcommunication devices, the first OFDMA PHY data unit having beentransmitted by a third communication device, wherein data correspondingto the first communication device is in included in the first OFDMA PHYdata unit in a first frequency subband within a communication channelspanned by the first OFDMA PHY data unit; determining, at the firstcommunication device, a second frequency subband in which the firstcommunication device is to transmit as part of a second OFDMA PHY dataunit, the second OFDMA PHY data unit for acknowledging, by the firstcommunication device and one or more second communication devices, thefirst OFDMA PHY data unit, wherein the second frequency subband isdetermined based on i) a number of the first communication device andthe one or more second communication devices, and ii) a number ofcomponent communication channels spanned by the first OFDMA PHY dataunit; generating, at the first communication device, a portion of thesecond OFDMA PHY data unit so that the portion of the second OFDMA PHYdata unit corresponds to the second frequency subband; and transmitting,at the first communication device, the portion of the second OFDMA PHYdata unit while the one or more second communication devices transmitone or more other portions of the second OFDMA PHY data unit toacknowledge the first OFDMA PHY data unit.

In other embodiments, the method includes any suitable combination ofone or more of the following features.

The second frequency subband is determined further based on a positionof the first frequency subband within the communication channel spannedby the first OFDMA PHY data unit.

Determining the second frequency subband comprises: determining aninteger part of a division of i) the number of component communicationchannels spanned by the first OFDMA PHY data unit by ii) the number ofthe first communication device and the one or more second communicationdevices; and determining a remainder of the division; wherein the secondfrequency subband is determined using the integer part of the divisionand the remainder.

The integer part and the remainder of the division of i) the number ofcomponent communication channels spanned by the first OFDMA PHY dataunit by ii) the number of the first communication device and the one ormore second communication devices is determined when the number ofcomponent communication channels spanned by the first OFDMA PHY dataunit is greater than or equal to the number of the first communicationdevice and the one or more second communication devices.

Determining the second frequency subband comprises: determining aninteger part of a division of i) the number of the first communicationdevice and the one or more second communication devices by ii) thenumber of component communication channels spanned by the first OFDMAPHY data unit; and determining a remainder of the division; wherein thesecond frequency subband is determined using the integer part of thedivision and the remainder.

The integer part and the remainder of the division of i) the number ofthe first communication device and the one or more second communicationdevices by ii) the number of component communication channels spanned bythe first OFDMA PHY data unit is determined when the number of componentcommunication channels spanned by the first OFDMA PHY data unit is lessthan the number of the first communication device and the one or moresecond communication devices.

In another embodiment, an apparatus comprises: a network interfacedevice having one or more integrate circuits configured to: receive afirst OFDMA PHY data unit, the first OFDMA PHY data unit havingindependent data for a first communication device and one or more secondcommunication devices, the first OFDMA PHY data unit having beentransmitted by a third communication device, wherein data correspondingto the first communication device is in included in the first OFDMA PHYdata unit in a first frequency subband within a communication channelspanned by the first OFDMA PHY data unit, determine a second frequencysubband in which the first communication device is to transmit as partof a second OFDMA PHY data unit, the second OFDMA PHY data unit foracknowledging, by the first communication device and one or more secondcommunication devices, the first OFDMA PHY data unit, wherein the secondfrequency subband is determined based on i) a number of the firstcommunication device and the one or more second communication devices,and ii) a number of component communication channels spanned by thefirst OFDMA PHY data unit, generate a portion of the second OFDMA PHYdata unit so that the portion of the second OFDMA PHY data unitcorresponds to the second frequency subband, and transmit the portion ofthe second OFDMA PHY data unit while the one or more secondcommunication devices transmit one or more other portions of the secondOFDMA PHY data unit to acknowledge the first OFDMA PHY data unit.

In other embodiments, the apparatus includes any suitable combination ofone or more of the following features.

The one or more integrated circuit devices are configured to: determinethe second frequency subband further based on a position of the firstfrequency subband within the communication channel spanned by the firstOFDMA PHY data unit.

The one or more integrated circuit devices are configured to: determinean integer part of a division of i) the number of componentcommunication channels spanned by the first OFDMA PHY data unit by ii)the number of the first communication device and the one or more secondcommunication devices; determine a remainder of the division; anddetermine the second frequency subband using the integer part of thedivision and the remainder.

The integer part and the remainder of the division of i) the number ofcomponent communication channels spanned by the first OFDMA PHY dataunit by ii) the number of the first communication device and the one ormore second communication devices is determined when the number ofcomponent communication channels spanned by the first OFDMA PHY dataunit is greater than or equal to the number of the first communicationdevice and the one or more second communication devices.

The one or more integrated circuit devices are configured to: determinean integer part of a division of i) the number of the firstcommunication device and the one or more second communication devices byii) the number of component communication channels spanned by the firstOFDMA PHY data unit; determine a remainder of the division; anddetermine the second frequency subband using the integer part of thedivision and the remainder.

The integer part and the remainder of the division of i) the number ofthe first communication device and the one or more second communicationdevices by ii) the number of component communication channels spanned bythe first OFDMA PHY data unit is determined when the number of componentcommunication channels spanned by the first OFDMA PHY data unit is lessthan the number of the first communication device and the one or moresecond communication devices.

At least some of the various blocks, operations, and techniquesdescribed above may be implemented utilizing hardware, a processorexecuting firmware instructions, a processor executing softwareinstructions, or any combination thereof. When implemented utilizing aprocessor executing software or firmware instructions, the software orfirmware instructions may be stored in any tangible, non-transitorycomputer readable medium, or media, such as a magnetic disk, an opticaldisk, a RAM, a ROM, a flash memory, a magnetic tape, etc. The softwareor firmware instructions may include machine readable instructions that,when executed by one or more processors, cause the one or moreprocessors to perform various acts.

When implemented in hardware, the hardware may comprise one or more ofdiscrete components, one or more integrated circuits, one or moreapplication-specific integrated circuits (ASICs), one or moreprogrammable logic devices (PLDs), etc.

While the present invention has been described with reference tospecific examples, which are intended to be illustrative only and not tobe limiting of the invention, changes, additions and/or deletions may bemade to the disclosed embodiments without departing from the scope ofthe invention.

What is claimed is:
 1. A method for communicating in a wirelesscommunication network, the method comprising: generating, at a firstcommunication device, respective media access control (MAC) protocoldata units (MPDUs), each MPDU including respective data for a respectivesecond communication device among a plurality of second communicationdevices; determining, at the first communication device, respectiveresource units (RUs) via which at least some of the second communicationdevices are to transmit as part of an uplink (UL) orthogonal frequencydivision multiple access (OFDMA) physical layer (PHY) transmission torespectively acknowledge receipt of the respective MPDUs, wherein therespective RUs correspond to respective frequency portions of acommunication channel; generating, at the first communication device,respective control frames corresponding to at least some of the secondcommunication devices, wherein the respective control frames areconfigured to prompt the at least some of the second communicationdevices to transmit the UL OFDMA PHY transmission, and wherein thecontrol frames include indicators of the RUs via which the at least someof the second communication devices are to transmit as part of the ULOFDMA PHY transmission; generating, at the first communication device, asingle multi user (MU) PHY data unit that includes i) the MPDUs, and ii)the control frames; transmitting, by the first communication device andto the plurality of second communication devices, the single MU PHY dataunit; receiving, at the first communication device, the UL OFDMA PHYtransmission from the at least some of the second communication devices,the UL OFDMA PHY transmission corresponding to an acknowledgment of atleast some of the MPDUs by the at least some of the second communicationdevices, wherein the UL OFDMA PHY transmission includes respectivetransmissions from respective second communication devices viarespective RUs indicated by the control frames in the single MU PHY dataunit; and processing, at the first communication device, the UL OFDMAPHY data unit to determine whether the at least some of the secondcommunication devices received the respective MPDUs.